New mathematical rules

.settings/org.eclipse.core.resources.prefs

@@ -8,5 +8,6 @@ encoding//src/org/warp/picalculator/math/MathematicalSymbols.java=UTF-8
 encoding//src/org/warp/picalculator/math/functions/Expression.java=UTF-8
 encoding//src/org/warp/picalculator/math/functions/Root.java=UTF-8
 encoding//src/org/warp/picalculator/math/functions/RootSquare.java=UTF-8
+encoding//src/org/warp/picalculator/math/functions/Sum.java=UTF-8
 encoding//src/org/warp/picalculator/screens/EquationScreen.java=UTF-8
 encoding/<project>=UTF-8

.settings/org.eclipse.jdt.core.prefs

@@ -0,0 +1,12 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.methodParameters=do not generate
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=1.8
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.8

src/org/nevec/rjm/NumeroAvanzatoVec.java

@@ -512,6 +512,17 @@ public class NumeroAvanzatoVec implements Comparable<NumeroAvanzatoVec> {
 		return (this.terms.size() <= 1);
 	}
 
+
+
+	public boolean hasVariables() {
+		for (NumeroAvanzato s : terms) {
+			if ((s.getVariableX().count() | s.getVariableY().count() | s.getVariableZ().count()) != 0) {
+				return true;
+			}
+		}
+		return false;
+	}
+	
 	/**
 	 * True if the value is BigInteger. Equivalent to the indication whether a
 	 * conversion to a BigInteger can be exact.

src/org/warp/picalculator/Main.java

@@ -48,13 +48,6 @@ public class Main {
 	}
 
 	public static void main(String[] args) throws InterruptedException {
-		if (test()) {
-			return;
-		}
 		new Main();
 	}
-	
-	private static boolean test() {
-		return false;
-	}
 }

src/org/warp/picalculator/Utils.java

@@ -2,6 +2,8 @@ package org.warp.picalculator;
 
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawLine;
 
+import com.rits.cloning.Cloner;
+
 import java.awt.Font;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -44,6 +46,8 @@ public class Utils {
 
 	public static boolean debugOn;
 
+	public static Cloner cloner = new Cloner();
+	
 	public static final class DebugStream extends StringWriter {
 
 		public void println(String str) {
@@ -68,13 +72,30 @@ public class Utils {
 		return contains;
 	}
 
+	private static final String[] regexNormalSymbols = new String[]{"\\", ".", "[", "]", "{", "}", "(", ")", "*", "+", "-", "?", "^", "$", "|"};
+	
 	public static String ArrayToRegex(String[] array) {
 		String regex = null;
 		for (String symbol : array) {
-			if (regex != null) {
+			boolean contained = false;
-				regex += "|\\" + symbol;
+			for (String smb : regexNormalSymbols) {
+				if (smb.equals(symbol)) {
+					contained = true;
+					break;
+				}
+			}
+			if (contained) {
+				if (regex != null) {
+					regex += "|\\" + symbol;
+				} else {
+					regex = "\\" + symbol;
+				}
 			} else {
-				regex = "\\" + symbol;
+				if (regex != null) {
+					regex += "|" + symbol;
+				} else {
+					regex = symbol;
+				}
 			}
 		}
 		return regex;
@@ -99,7 +120,7 @@ public class Utils {
 
 	public static boolean areThereOnlySettedUpFunctionsSumsEquationsAndSystems(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
+			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Subtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
 				if (fl.get(i) instanceof AnteriorFunction) {
 					if (((AnteriorFunction) fl.get(i)).getVariable() == null) {
 						return false;
@@ -118,7 +139,7 @@ public class Utils {
 
 	public static boolean areThereOnlySettedUpFunctionsSumsMultiplicationsEquationsAndSystems(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
+			if (!(fl.get(i) instanceof Number || fl.get(i) instanceof Multiplication || fl.get(i) instanceof PrioritaryMultiplication || fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Subtraction || fl.get(i) instanceof Equation || fl.get(i) instanceof EquationsSystemPart || fl.get(i) instanceof Expression)) {
 				if (fl.get(i) instanceof AnteriorFunction) {
 					if (((AnteriorFunction) fl.get(i)).getVariable() == null) {
 						return false;
@@ -220,7 +241,7 @@ public class Utils {
 
 	public static boolean areThereEmptySums(ArrayList<Function> fl) {
 		for (int i = 0; i < fl.size(); i++) {
-			if (fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction) {
+			if (fl.get(i) instanceof Sum || fl.get(i) instanceof SumSubtraction || fl.get(i) instanceof Subtraction) {
 				if (((FunctionTwoValues) fl.get(i)).getVariable1() == null && ((FunctionTwoValues) fl.get(i)).getVariable2() == null) {
 					return true;
 				}
@@ -358,17 +379,21 @@ public class Utils {
 	}
 
 	public static final RAWFont getFont(boolean small, boolean zoomed) {
+		return PIDisplay.fonts[getFontIndex(small, zoomed)];
+	}
+
+	public static final int getFontIndex(boolean small, boolean zoomed) {
 		if (small) {
 			if (zoomed) {
-				return PIDisplay.fonts[3];
+				return 3;
 			} else {
-				return PIDisplay.fonts[1];
+				return 1;
 			}
 		} else {
 			if (zoomed) {
-				return PIDisplay.fonts[2];
+				return 2;
 			} else {
-				return PIDisplay.fonts[0];
+				return 0;
 			}
 		}
 	}

src/org/warp/picalculator/device/Keyboard.java

@@ -454,7 +454,7 @@ public class Keyboard {
 				refresh = true;
 			}
 			if (refresh) {
-				Display.repaint(true);
+				Display.repaint();
 			}
 		}
 	}
@@ -478,7 +478,7 @@ public class Keyboard {
 				}
 			}
 			if (refresh) {
-				Display.repaint(true);
+				Display.repaint();
 			}
 		}
 	}

src/org/warp/picalculator/device/PIDisplay.java

@@ -33,7 +33,7 @@ public final class PIDisplay {
 
 	private int[] skin;
 	private int[] skinSize;
-	public static RAWFont[] fonts = new RAWFont[4];
+	public static RAWFont[] fonts;
 
 	public static String error = null;
 	public String[] errorStackTrace = null;
@@ -45,7 +45,7 @@ public final class PIDisplay {
 	public PIDisplay(Screen screen) {
 		setScreen(screen);
 		INSTANCE = this;
-		run();
+		loop();
 	}
 	/*
 	 * private void load_skin() {
@@ -100,6 +100,30 @@ public final class PIDisplay {
 			System.exit(0);
 		}
 	}
+	
+	public void replaceScreen(Screen screen) {
+		if (screen.initialized == false) {
+			if (screen.canBeInHistory) {
+				Calculator.sessions[Calculator.currentSession] = screen;
+			} else {
+				Calculator.currentSession = -1;
+				for (int i = 0; i < Calculator.sessions.length - 2; i++) {
+					Calculator.sessions[i] = Calculator.sessions[i + 1];
+				}
+			}
+		}
+		screen.d = this;
+		try {
+			screen.create();
+			PIDisplay.screen = screen;
+			if (screen.initialized == false) {
+				screen.initialize();
+			}
+		} catch (Exception e) {
+			e.printStackTrace();
+			System.exit(0);
+		}
+	}
 
 	public boolean canGoBack() {
 		if (Calculator.currentSession == -1) {
@@ -176,6 +200,7 @@ public final class PIDisplay {
 	}
 
 	private void load_fonts() {
+		fonts = new RAWFont[7];
 		fonts[0] = new RAWFont();
 		fonts[0].create("big");
 		fonts[1] = new RAWFont();
@@ -184,7 +209,11 @@ public final class PIDisplay {
 		fonts[2].create("big_2x");
 		fonts[3] = new RAWFont();
 		fonts[3].create("small_2x");
-		setFont(fonts[0]);
+		fonts[4] = new RAWFont();
+		fonts[4].create("32");
+		fonts[5] = new RAWFont();
+		fonts[5].create("square");
+		glSetFont(fonts[0]);
 	}
 
 	private void draw_init() {
@@ -280,7 +309,7 @@ public final class PIDisplay {
 		glColor3f(255, 255, 255);
 
 		if (error != null) {
-			setFont(Utils.getFont(false, false));
+			glSetFont(Utils.getFont(false, false));
 			glColor3f(129, 28, 22);
 			glDrawStringRight(Main.screenSize[0] - 2, Main.screenSize[1]- this.glyphsHeight[1] - 2, "ANDREA CAVALLI'S CALCULATOR");
 			glColor3f(149, 32, 26);
@@ -291,7 +320,7 @@ public final class PIDisplay {
 				glDrawStringLeft(2, 22 + i, stackPart);
 				i += 11;
 			}
-			setFont(fonts[0]);
+			glSetFont(fonts[0]);
 			glColor3f(129, 28, 22);
 			glDrawStringCenter((Main.screenSize[0] / 2), 11, "UNEXPECTED EXCEPTION");
 		} else {
@@ -308,16 +337,13 @@ public final class PIDisplay {
 
 	private long precTime = -1;
 
-	public void refresh(boolean forced) {
+	public void refresh() {
 		float dt = 0;
 		long newtime = System.nanoTime();
 		if (precTime == -1) {
 			dt = 0;
 		} else {
 			dt = (float) ((newtime - precTime) / 1000000000d);
-			if (dt < 0.03 && !forced) {
-				return;
-			}
 		}
 		precTime = newtime;
 		/*
@@ -327,7 +353,7 @@ public final class PIDisplay {
 
 		screen.beforeRender(dt);
 		
-		if(forced==true || screen.mustBeRefreshed()) {
+		if(dt >= 0.03 | screen.mustBeRefreshed()) {
 			draw();
 		}
 
@@ -340,7 +366,7 @@ public final class PIDisplay {
 		}
 	};
 	
-	public void run() {
+	public void loop() {
 		try {
 			load_skin();
 			load_fonts();
@@ -359,10 +385,10 @@ public final class PIDisplay {
 
 			double extratime = 0;
 			while (Display.initialized) {
-				long start = System.nanoTime();
+				long start = System.currentTimeMillis();
-				Display.repaint(false);
+				Display.repaint();
-				long end = System.nanoTime();
+				long end = System.currentTimeMillis();
-				double delta = (end - start) / 1000000000;
+				double delta = (end - start) / 1000d;
 				int deltaInt = (int) Math.floor(delta);
 				int extraTimeInt = (int) Math.floor(extratime);
 				if (extraTimeInt + deltaInt < 50) {

src/org/warp/picalculator/device/graphicengine/Display.java

@@ -7,15 +7,15 @@ import java.awt.image.DataBufferInt;
 import java.util.ArrayList;
 
 import org.warp.picalculator.Main;
+import org.warp.picalculator.Utils;
 import org.warp.picalculator.device.PIDisplay;
-import org.warp.picalculator.device.PIFrame;
 
 public class Display {
 
-	private static PIFrame INSTANCE = new PIFrame();
+	private static Frame INSTANCE = new Frame();
 	public static int[] size = new int[] { 1, 1 };
-	public static BufferedImage g = new BufferedImage(size[0], size[1], BufferedImage.TYPE_INT_ARGB);
+	public static BufferedImage g = new BufferedImage(size[0], size[1], BufferedImage.TYPE_INT_RGB);
-	private static int[] canvas2d = new int[1];
+	static int[] canvas2d = new int[1];
 	public static int color = 0xFF000000;
 	public static boolean initialized = false;
 
@@ -38,6 +38,7 @@ public class Display {
 	}
 
 	public static void create() {
+		Display.setResizable(Utils.debugOn);
 		Display.setDisplayMode(Main.screenSize[0], Main.screenSize[1]);
 		INSTANCE.setVisible(true);
 		initialized = true;
@@ -74,38 +75,14 @@ public class Display {
 	@Deprecated()
 	public static void refresh() {
 		if (PIDisplay.screen == null || (PIDisplay.error != null && PIDisplay.error.length() > 0) || PIDisplay.screen == null || PIDisplay.screen.mustBeRefreshed()) {
-			Display.INSTANCE.c.forcerefresh = false;
 			Display.INSTANCE.c.repaint();
 		}
 	}
 
-	public static void repaint(boolean force) {
+	public static void repaint() {
-		Display.INSTANCE.c.forcerefresh = force;
 		Display.INSTANCE.c.repaint();
 	}
 
-//	private static ArrayList<Double> mediaValori = new ArrayList<Double>();
-	
-	public static void update(Graphics g, boolean forcerefresh) {
-//		long time1 = System.nanoTime();
-		PIDisplay.INSTANCE.refresh(forcerefresh);
-
-        final int[] a = ((DataBufferInt) Display.g.getRaster().getDataBuffer()).getData();
-//	        System.arraycopy(canvas2d, 0, a, 0, canvas2d.length);
-        canvas2d = a;
-		g.clearRect(0, 0, size[0], size[1]);
-		g.drawImage(Display.g, 0, 0, null);
-//		long time2 = System.nanoTime();
-//		double timeDelta = ((double)(time2-time1))/1000000000d;
-//		double mediaAttuale = timeDelta;
-//		mediaValori.add(mediaAttuale);
-//		double somma = 0;
-//		for (Double val : mediaValori) {
-//			somma+=val;
-//		}
-//		System.out.println(somma/((double)mediaValori.size()));
-	}
-
 	public static abstract class Startable {
 		public Startable() {
 			this.force = false;
@@ -286,20 +263,20 @@ public class Display {
 		}
 
 		public static void glDrawStringCenter(int x, int y, String text) {
-			glDrawStringLeft(x - (getStringWidth(text) / 2), y, text);
+			glDrawStringLeft(x - (glGetStringWidth(text) / 2), y, text);
 		}
 
 		public static void glDrawStringRight(int x, int y, String text) {
-			glDrawStringLeft(x - getStringWidth(text), y, text);
+			glDrawStringLeft(x - glGetStringWidth(text), y, text);
 		}
 
-		public static void setFont(RAWFont font) {
+		public static void glSetFont(RAWFont font) {
 			if (currentFont != font) {
 				currentFont = font;
 			}
 		}
 
-		public static int getStringWidth(String text) {
+		public static int glGetStringWidth(String text) {
 			int w =(currentFont.charW+1)*text.length();
 			if (text.length() > 0) {
 				return w-1;
@@ -309,11 +286,21 @@ public class Display {
 			// return text.length()*6;
 		}
 
-		public static int getWidth(FontMetrics fm, String text) {
+		public static int glGetStringWidth(RAWFont rf, String text) {
+			int w =(rf.charW+1)*text.length();
+			if (text.length() > 0) {
+				return w-1;
+			} else {
+				return 0;
+			}
+			// return text.length()*6;
+		}
+
+		public static int glGetFontWidth(FontMetrics fm, String text) {
 			return fm.stringWidth(text);
 		}
 
-		public static int getFontHeight() {
+		public static int glGetCurrentFontHeight() {
 			return currentFont.charH;
 		}
 

src/org/warp/picalculator/device/graphicengine/Frame.java

@@ -1,9 +1,10 @@
-package org.warp.picalculator.device;
+package org.warp.picalculator.device.graphicengine;
 
+import java.awt.AlphaComposite;
 import java.awt.Cursor;
 import java.awt.Dimension;
-import java.awt.Frame;
 import java.awt.Graphics;
+import java.awt.Graphics2D;
 import java.awt.Point;
 import java.awt.Toolkit;
 import java.awt.event.ComponentEvent;
@@ -11,23 +12,26 @@ import java.awt.event.ComponentListener;
 import java.awt.event.KeyEvent;
 import java.awt.event.KeyListener;
 import java.awt.image.BufferedImage;
+import java.awt.image.DataBufferInt;
+import java.util.ArrayList;
 
 import javax.swing.JFrame;
 import javax.swing.JPanel;
 
 import org.warp.picalculator.Main;
 import org.warp.picalculator.Utils;
+import org.warp.picalculator.device.Keyboard;
+import org.warp.picalculator.device.PIDisplay;
 import org.warp.picalculator.device.Keyboard.Key;
-import org.warp.picalculator.device.graphicengine.Display;
 
-public class PIFrame extends JFrame {
+public class Frame extends JFrame {
 	private static final long serialVersionUID = 2945898937634075491L;
 	public CustomCanvas c;
 	public boolean wasResized = false;
 
-	public PIFrame() {
+	public Frame() {
 		c = new CustomCanvas();
-		c.setDoubleBuffered(true);
+		c.setDoubleBuffered(false);
 		this.add(c);
 //		this.setExtendedState(Frame.MAXIMIZED_BOTH);
 		Toolkit.getDefaultToolkit().setDynamicLayout(false);
@@ -432,6 +436,8 @@ public class PIFrame extends JFrame {
 		return c.getHeight();
 	}
 
+//	private static ArrayList<Double> mediaValori = new ArrayList<Double>();
+
 	public static class CustomCanvas extends JPanel {
 
 		/**
@@ -440,16 +446,24 @@ public class PIFrame extends JFrame {
 		private static final long serialVersionUID = 605243927485370885L;
 
 		@Override
-		public void paintComponent(Graphics graphics) {
+		public void paintComponent(Graphics g) {
-			Display.update(graphics, forcerefresh);
+//			long time1 = System.nanoTime();
-		}
+			PIDisplay.INSTANCE.refresh();
 
-		@Override
+	        final int[] a = ((DataBufferInt) Display.g.getRaster().getDataBuffer()).getData();
-		public void repaint() {
+//		        System.arraycopy(canvas2d, 0, a, 0, canvas2d.length);
-			forcerefresh = false;
+	        Display.canvas2d = a;
-			super.repaint();
+			g.clearRect(0, 0, Display.size[0], Display.size[1]);
+			g.drawImage(Display.g, 0, 0, null);
+//			long time2 = System.nanoTime();
+//			double timeDelta = ((double)(time2-time1))/1000000000d;
+//			double mediaAttuale = timeDelta;
+//			mediaValori.add(mediaAttuale);
+//			double somma = 0;
+//			for (Double val : mediaValori) {
+//				somma+=val;
+//			}
+//			System.out.println(somma/((double)mediaValori.size()));
 		}
-
-		public boolean forcerefresh = false;
 	}
 }

src/org/warp/picalculator/device/graphicengine/RAWFont.java

@@ -52,9 +52,6 @@ public class RAWFont {
         			currentBit += 1;
             	}
             } else {
-            	if (charIndex == 65 && name == "big_2x") {
-            		System.out.println("test");
-            	}
             	int currentInt = 0;
             	int currentBit = 0;
             	for (int i = 0; i < charS; i++) {
@@ -81,18 +78,18 @@ public class RAWFont {
 		int[] file = Utils.realBytes(Utils.convertStreamToByteArray(res.openStream(), res.getFile().length()));
 		int filelength = file.length;
 		if (filelength >= 16) {
-			if (file[0x0] == 114 && file[0x1] == 97 && file[0x2] == 119 && file[0x3] == 0xFF && file[0x6] == 0xFF && file[0xB] == 0xFF) {
+			if (file[0x0] == 114 && file[0x1] == 97 && file[0x2] == 119 && file[0x3] == 0xFF && file[0x8] == 0xFF && file[0xD] == 0xFF) {
-				charW = file[0x4];
+				charW = file[0x4] << 8 | file[0x5];
-				charH = file[0x5];
+				charH = file[0x6] << 8 | file[0x7];
 				charS = charW*charH;
 				charIntCount = (int) Math.ceil(((double)charS)/((double)intBits));
-				minBound = file[0x7] << 24 | file[0x8] << 16 | file[0x9] << 8 | file[0xA];
+				minBound = file[0x9] << 24 | file[0xA] << 16 | file[0xB] << 8 | file[0xC];
-				maxBound = file[0xC] << 24 | file[0xD] << 16 | file[0xE] << 8 | file[0xF];
+				maxBound = file[0xE] << 24 | file[0xF] << 16 | file[0x10] << 8 | file[0x11];
 				if (maxBound <= minBound) {
 					maxBound = 10000; //TODO remove it: temp fix
 				}
 		        rawchars = new boolean[maxBound-minBound][];
-		        int index = 0x10;
+		        int index = 0x12;
 		        while (index < filelength) {
 		        	try {
 			        	int charIndex = file[index] << 8 | file[index+1];

src/org/warp/picalculator/math/Calculator.java

@@ -11,6 +11,7 @@ import org.warp.picalculator.Error;
 import org.warp.picalculator.Errors;
 import org.warp.picalculator.Utils;
 import org.warp.picalculator.device.PIDisplay;
+import org.warp.picalculator.device.graphicengine.Display;
 import org.warp.picalculator.device.graphicengine.Screen;
 import org.warp.picalculator.math.functions.Expression;
 import org.warp.picalculator.math.functions.Function;
@@ -33,7 +34,7 @@ public class Calculator {
 				throw new Error(Errors.SYNTAX_ERROR);
 			}
 			String[] parts = string.substring(1).split("\\{");
-			EquationsSystem s = new EquationsSystem();
+			EquationsSystem s = new EquationsSystem(null);
 			for (String part : parts) {
 				s.addVariableToEnd(parseEquationString(part));
 			}
@@ -41,63 +42,67 @@ public class Calculator {
 		} else if (string.contains("=")) {
 			return parseEquationString(string);
 		} else {
-			return new Expression(string);
+			return new Expression(null, string);
 		}
 	}
 	
 	public static Function parseEquationString(String string) throws Error {
 		String[] parts = string.split("=");
 		if (parts.length == 1) {
-			return new Equation(new Expression(parts[0]), new Number(NumeroAvanzato.ZERO));
+			Equation e = new Equation(null, null, null);
+			e.setVariable1(new Expression(e, parts[0]));
+			e.setVariable2(new Number(e, NumeroAvanzato.ZERO));
+			return e;
 		} else if (parts.length == 2) {
-			return new Equation(new Expression(parts[0]), new Expression(parts[1]));
+			Equation e = new Equation(null, null, null);
+			e.setVariable1(new Expression(e, parts[0]));
+			e.setVariable2(new Expression(e, parts[1]));
+			return e;
 		} else {
 			throw new Error(Errors.SYNTAX_ERROR);
 		}
 	}
 
-	public static void solve() throws Error {
+	public static void solve(EquationScreen es) throws Error {
-		if (Calculator.currentSession == 0 && Calculator.sessions[0] instanceof EquationScreen) {
+		List<Function> results = new ArrayList<>();
-			EquationScreen es = (EquationScreen) Calculator.sessions[0];
+		List<Function> partialResults = new ArrayList<>();
-			List<Function> results = new ArrayList<>();
+		for (Function f : es.f) {
-			List<Function> partialResults = new ArrayList<>();
+			if (f instanceof Equation) {
-			for (Function f : es.f) {
+				PIDisplay.INSTANCE.setScreen(new SolveEquationScreen(es));
-				if (f instanceof Equation) {
+			} else {
-					PIDisplay.INSTANCE.setScreen(new SolveEquationScreen(es));
+				results.add(f);
-				} else {
+				while (Utils.allSolved(results) == false) {
-					results.add(f);
+					for (Function itm : results) {
-					while (Utils.allSolved(results) == false) {
+						if (itm.isSolved() == false) {
-						for (Function itm : results) {
+							List<Function> dt = itm.solveOneStep();
-							if (itm.isSolved() == false) {
+							partialResults.addAll(dt);
-								List<Function> dt = itm.solveOneStep();
+						} else {
-								partialResults.addAll(dt);
+							partialResults.add(itm);
-							} else {
-								partialResults.add(itm);
-							}
 						}
-						results = new ArrayList<Function>(partialResults);
-						partialResults.clear();
 					}
+					results = new ArrayList<Function>(partialResults);
+					partialResults.clear();
 				}
 			}
-			if (results.size() == 0) {
+		}
-				
+		if (results.size() == 0) {
-			} else {
+			es.resultsCount = 0;
-				Collections.reverse(results);
+		} else {
-//				// add elements to al, including duplicates
+			es.resultsCount = results.size();
-//				Set<Function> hs = new LinkedHashSet<>();
+			Collections.reverse(results);
-//				hs.addAll(results);
+			// add elements to al, including duplicates
-//				results.clear();
+			Set<Function> hs = new LinkedHashSet<>();
-//				results.addAll(hs);
+			hs.addAll(results);
-				es.f2 = results;
+			results.clear();
-				for (Function rf : es.f2) {
+			results.addAll(hs);
-					rf.generateGraphics();
+			es.f2 = results;
-				}
+			for (Function rf : es.f2) {
+				rf.generateGraphics();
 			}
 		}
 	}
 	
-	public static void solve(char letter) throws Error {
+	public static void solve(EquationScreen equationScreen, char letter) throws Error {
 		if (Calculator.currentSession == 0 && Calculator.sessions[0] instanceof EquationScreen) {
 			EquationScreen es = (EquationScreen) Calculator.sessions[0];
 			List<Function> f = es.f;
@@ -117,7 +122,7 @@ public class Calculator {
 		}
 	}
 
-	public static void simplify() {
+	public static void simplify(EquationScreen equationScreen) {
 		
 	}
 

src/org/warp/picalculator/math/MathematicalSymbols.java

@@ -7,7 +7,8 @@ import org.warp.picalculator.Utils;
 public class MathematicalSymbols {
 	public static final String SUM = "+";
 	public static final String SUM_SUBTRACTION = "±";
-	public static final String SUBTRACTION = "-";
+	public static final String SUBTRACTION = "−";
+	public static final String MINUS = "-";
 	public static final String MULTIPLICATION = "*";
 	public static final String PRIORITARY_MULTIPLICATION = "▪";
 	public static final String DIVISION = "/";
@@ -28,11 +29,11 @@ public class MathematicalSymbols {
 	}
 
 	public static final String[] functionsSN() {
-		return new String[] { SQUARE_ROOT };
+		return new String[] { SQUARE_ROOT, MINUS };
 	}
 
 	public static final String[] signums(boolean withMultiplication, boolean withPrioritaryMultiplication) {
-		String[] ret = new String[] { SUM, SUM_SUBTRACTION, DIVISION };
+		String[] ret = new String[] { SUM, SUM_SUBTRACTION, SUBTRACTION, DIVISION };
 		if (withMultiplication) {
 			ret = Utils.add(ret, MULTIPLICATION);
 		}
@@ -47,7 +48,7 @@ public class MathematicalSymbols {
 	}
 
 	public static String[] variables() {
-		return new String[] { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "♓"};
+		return new String[] { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"};
 	}
 
 	public static String[] genericSyntax() {

src/org/warp/picalculator/math/functions/AnteriorFunction.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 
 import java.util.List;
@@ -14,16 +14,18 @@ import org.warp.picalculator.device.graphicengine.Display;
 import com.rits.cloning.Cloner;
 
 public abstract class AnteriorFunction implements Function {
-	public AnteriorFunction(Function value) {
+	public AnteriorFunction(Function parent, Function value) {
+		setParent(parent);
 		setVariable(value);
 	}
 
-	protected Function variable = new Number(NumeroAvanzatoVec.ZERO);
+	protected Function parent;
+	protected Function variable = new Number(null, NumeroAvanzatoVec.ZERO);
 	protected int width;
 	protected int height;
 	protected int line;
 	protected boolean small;
-	
+
 	public Function getVariable() {
 		return variable;
 	}
@@ -32,6 +34,15 @@ public abstract class AnteriorFunction implements Function {
 		variable = value;
 	}
 
+	public Function getParent() {
+		return parent;
+	}
+
+	public Function setParent(Function value) {
+		parent = value;
+		return this;
+	}
+
 	@Override
 	public abstract String getSymbol();
 
@@ -50,7 +61,7 @@ public abstract class AnteriorFunction implements Function {
 		variable.setSmall(small);
 		variable.generateGraphics();
 		
-		width = getStringWidth(getSymbol()) + 1 + getVariable().getWidth();
+		width = glGetStringWidth(getSymbol()) + 1 + getVariable().getWidth();
 		height = variable.getHeight();
 		line = variable.getLine();
 	}
@@ -58,10 +69,10 @@ public abstract class AnteriorFunction implements Function {
 	@Override
 	public void draw(int x, int y) {
 		float h1 = getVariable().getHeight();
-		int wsegno = getStringWidth(getSymbol());
+		int wsegno = glGetStringWidth(getSymbol());
 		float hsegno = Utils.getFontHeight(small);
 		float maxh = getHeight();
-		Display.Render.setFont(Utils.getFont(small));
+		Display.Render.glSetFont(Utils.getFont(small));
 		
 		glDrawStringLeft(x, (int) Math.floor(y + (maxh - hsegno) / 2), getSymbol());
 		getVariable().draw(x + wsegno + 1, (int) Math.floor(y + (maxh - h1) / 2));

src/org/warp/picalculator/math/functions/Division.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glColor3f;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glFillRect;
@@ -16,11 +16,17 @@ import org.warp.picalculator.device.PIDisplay;
 import org.warp.picalculator.device.graphicengine.Display;
 import org.warp.picalculator.device.graphicengine.Display.Render;
 import org.warp.picalculator.math.MathematicalSymbols;
+import org.warp.picalculator.math.rules.FractionsRule1;
+import org.warp.picalculator.math.rules.FractionsRule2;
+import org.warp.picalculator.math.rules.FractionsRule3;
+import org.warp.picalculator.math.rules.NumberRule1;
+import org.warp.picalculator.math.rules.NumberRule2;
+import org.warp.picalculator.math.rules.UndefinedRule2;
 
 public class Division extends FunctionTwoValues {
 
-	public Division(Function value1, Function value2) {
+	public Division(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -31,21 +37,24 @@ public class Division extends FunctionTwoValues {
 
 	@Override
 	protected boolean isSolvable() throws Error {
-		if (variable1 instanceof Number & variable2 instanceof Number) {
+		if (FractionsRule1.compare(this)) return true;
-			if (((Number)variable2).getTerm().compareTo(NumeroAvanzatoVec.ZERO) == 0) {
+		if (FractionsRule2.compare(this)) return true;
-				throw new Error(Errors.DIVISION_BY_ZERO);
+		if (FractionsRule3.compare(this)) return true;
-			} else {
+		if (UndefinedRule2.compare(this)) return true;
-				return true;
-			}
-		}
 		return false;
 	}
 	
 	@Override
 	public List<Function> solveOneStep() throws Error {
 		ArrayList<Function> result = new ArrayList<>();
-		if (variable1.isSolved() & variable2.isSolved()) {
+		if (FractionsRule1.compare(this)) {
-			result.add(((Number) variable1).divide((Number)variable2));
+			result = FractionsRule1.execute(this);
+		} else if (FractionsRule2.compare(this)) {
+			result = FractionsRule2.execute(this);
+		} else if (FractionsRule3.compare(this)) {
+			result = FractionsRule3.execute(this);
+		} else if (UndefinedRule2.compare(this)) {
+			result = UndefinedRule2.execute(this);
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
 			List<Function> l2 = new ArrayList<Function>();
@@ -63,7 +72,7 @@ public class Division extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Division((Function)f[0], (Function)f[1]));
+				result.add(new Division(this.parent, (Function)f[0], (Function)f[1]));
 			}
 		}
 		return result;
@@ -117,10 +126,10 @@ public class Division extends FunctionTwoValues {
 		}
 		int w1 = 0;
 		int h1 = 0;
-		Display.Render.setFont(Utils.getFont(small));
+		Display.Render.glSetFont(Utils.getFont(small));
 		if (minus) {
-			w1 = getStringWidth(numerator);
+			w1 = glGetStringWidth(numerator);
-			h1 = Render.getFontHeight();
+			h1 = Render.glGetCurrentFontHeight();
 		} else {
 			w1 = ((Function) var1).getWidth();
 			h1 = ((Function) var1).getHeight();
@@ -133,8 +142,8 @@ public class Division extends FunctionTwoValues {
 			maxw = 1 + w2;
 		}
 		if (minus && drawMinus) {
-			minusw = getStringWidth("-") + 1;
+			minusw = glGetStringWidth("-") + 1;
-			minush = Render.getFontHeight();
+			minush = Render.glGetCurrentFontHeight();
 			glDrawStringLeft(x+1, y + h1 + 1 + 1 - (minush / 2), "-");
 			glDrawStringLeft((int) (x+1 + minusw + 1 + (maxw - w1) / 2d), y, numerator);
 		} else {
@@ -189,7 +198,7 @@ public class Division extends FunctionTwoValues {
 		}
 		int w1 = 0;
 		if (minus) {
-			w1 = getStringWidth(numerator);
+			w1 = glGetStringWidth(numerator);
 		} else {
 			w1 = variable1.getWidth();
 		}
@@ -201,7 +210,7 @@ public class Division extends FunctionTwoValues {
 			maxw = w2+1;
 		}
 		if (minus && drawMinus) {
-			return 1 + getStringWidth("-") + 1 + maxw;
+			return 1 + glGetStringWidth("-") + 1 + maxw;
 		} else {
 			return 1 + maxw;
 		}

src/org/warp/picalculator/math/functions/EmptyNumber.java

@@ -0,0 +1,66 @@
+package org.warp.picalculator.math.functions;
+
+import java.util.List;
+
+import org.warp.picalculator.Error;
+import org.warp.picalculator.device.graphicengine.Display;
+
+public class EmptyNumber implements Function {
+
+	@Override
+	public String getSymbol() {
+		return " ";
+	}
+
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public boolean isSolved() throws Error {
+		return false;
+	}
+
+	@Override
+	public void generateGraphics() {
+
+	}
+
+	@Override
+	public void draw(int x, int y) {
+		Display.Render.glDrawStringLeft(x, y, " ");
+	}
+
+	@Override
+	public int getWidth() {
+		return Display.Render.glGetStringWidth(" ");
+	}
+
+	@Override
+	public int getHeight() {
+		return Display.Render.glGetCurrentFontHeight();
+	}
+
+	@Override
+	public int getLine() {
+		return Display.Render.glGetCurrentFontHeight()/2;
+	}
+
+	@Override
+	public Function setParent(Function parent) {
+		return null;
+	}
+
+	@Override
+	public Function getParent() {
+		return null;
+	}
+
+	@Override
+	public void setSmall(boolean small) {
+
+	}
+
+}

src/org/warp/picalculator/math/functions/Expression.java

@@ -20,31 +20,35 @@ import org.warp.picalculator.math.MathematicalSymbols;
 import org.warp.picalculator.math.Variable;
 import org.warp.picalculator.math.Variables;
 
+import sun.reflect.generics.reflectiveObjects.NotImplementedException;
+
 public class Expression extends FunctionMultipleValues {
 
-	public Expression() {
+	public Expression(Function parent) {
-		super();
+		super(parent);
 	}
-
+	
-	public Expression(Function[] values) {
+	public Expression(Function parent, Function[] values) {
-		super(values);
+		super(parent, values);
 	}
 
 	private boolean initialParenthesis = false;
+	private Function parent = null;
 
-	public Expression(String string) throws Error {
+	public Expression(Function parent, String string) throws Error {
-		this(string, "", true);
+		this(parent, string, "", true);
 	}
 
-	public Expression(String string, String debugSpaces, boolean initialParenthesis) throws Error {
+	public Expression(Function parent, String string, String debugSpaces, boolean initialParenthesis) throws Error {
-		super();
+		super(parent);
+		this.parent = parent;
 		this.initialParenthesis = initialParenthesis;
 		boolean isNumber = false;
 
 		// Determine if the expression is already a number:
 		// Determina se l'espressione è già un numero:
 		try {
-			new Number(string);
+			new Number(this, string);
 			isNumber = true;
 		} catch (NumberFormatException ex) {
 			isNumber = false;
@@ -53,10 +57,12 @@ public class Expression extends FunctionMultipleValues {
 		String processExpression = string;
 		Utils.debug.println(debugSpaces + "•Analyzing expression:" + processExpression);
 		
+		isNumber = false; //TODO: rimuovere isNumber, alcune semplificazione come la divisione per zero altrimenti verrebbero saltate.
+		
 		if (isNumber){
 			// If the expression is already a number:
 			// Se l'espressione è già un numero:
-			Number t = new Number(string);
+			Number t = new Number(this, string);
 			setVariables(new Function[] { t });
 			Utils.debug.println(debugSpaces + "•Result:" + t.toString());
 		} else {
@@ -95,7 +101,7 @@ public class Expression extends FunctionMultipleValues {
 			while (matcher.find()) {
 				symbolsChanged = true;
 				String correzione = "+";
-				processExpression = processExpression.substring(0, matcher.start(0) + 1) + correzione + processExpression.substring(matcher.start(0) + matcher.group(0).length(), processExpression.length());
+				processExpression = processExpression.substring(0, matcher.start(0)) + correzione + processExpression.substring(matcher.start(0) + matcher.group(0).length(), processExpression.length());
 				matcher = pattern.matcher(processExpression);
 			}
 
@@ -116,11 +122,12 @@ public class Expression extends FunctionMultipleValues {
 				processExpression = processExpression.replace("(+", "(");
 			}
 
-			// Cambia i segni appena prima le parentesi
+//			// Cambia i segni appena prima le parentesi
-			if (processExpression.contains("-(")) {
+//			if (processExpression.contains("-(")) {
-				symbolsChanged = true;
+//				symbolsChanged = true;
-				processExpression = processExpression.replace("-(", "-1*(");
+//				processExpression = processExpression.replace("-(", "-1*(");
-			}
+//			}
+
 			// Rimuovi i segni appena dopo l'inizio
 			if (processExpression.startsWith("+")) {
 				symbolsChanged = true;
@@ -137,25 +144,46 @@ public class Expression extends FunctionMultipleValues {
 				processExpression = processExpression.substring(0, matcher.start(0) + 1) + correzione + processExpression.substring(matcher.start(0) + matcher.group(0).length(), processExpression.length());
 				matcher = pattern.matcher(processExpression);
 			}
+			
+			// Correggi i segni - in −
+			processExpression = processExpression.replace("-", MathematicalSymbols.SUBTRACTION);
 
-			// Correggi i segni - in +-
+			// Correggi i segni − dopo di espressioni o funzioni SN in -
-			pattern = Pattern.compile("[^" + Utils.ArrayToRegex(concat(concat(MathematicalSymbols.functions(), new String[] { MathematicalSymbols.PARENTHESIS_OPEN }), MathematicalSymbols.signums(true, true))) + "]-");
+			pattern = Pattern.compile("[" + Utils.ArrayToRegex(concat(concat(concat(MathematicalSymbols.functions(), MathematicalSymbols.variables()), new String[] { MathematicalSymbols.PARENTHESIS_OPEN }), MathematicalSymbols.signums(true, true))) + "]" + MathematicalSymbols.SUBTRACTION);
 			matcher = pattern.matcher(processExpression);
 			while (matcher.find()) {
 				symbolsChanged = true;
-				String correzione = "+-";
+				String correzione = MathematicalSymbols.MINUS;
-				processExpression = processExpression.substring(0, matcher.start(0) + 1) + correzione + processExpression.substring(matcher.start(0) + matcher.group(0).length(), processExpression.length());
+				processExpression = processExpression.substring(0, matcher.start(0) + 1) + correzione + processExpression.substring(matcher.start(0) + 2, processExpression.length());
 				matcher = pattern.matcher(processExpression);
 			}
+			
+			// Cambia il segno iniziale − in -
+			if (processExpression.startsWith("−")) {
+				symbolsChanged = true;
+				processExpression = "-" + processExpression.substring(1, processExpression.length());
+			}
 
 			if (symbolsChanged) {
 				Utils.debug.println(debugSpaces + "•Resolved signs:" + processExpression);
 			}
 
+			// Aggiungi le parentesi implicite per le potenze con una incognita
+			pattern = Pattern.compile("(?<!(?:\\(|^))(["+Utils.ArrayToRegex(MathematicalSymbols.variables())+"]+"+MathematicalSymbols.POWER+"[^" + Utils.ArrayToRegex(Utils.add(concat(MathematicalSymbols.functionsNSN(), concat(MathematicalSymbols.signums(true, true), MathematicalSymbols.genericSyntax())), ")")) + "])(?!\\))");
+			matcher = pattern.matcher(processExpression);
+			symbolsChanged = false;
+			while (matcher.find()) {
+				symbolsChanged = true;
+				String correzione = "("+matcher.group().replace(MathematicalSymbols.POWER, "⑴")+")";
+				processExpression = processExpression.substring(0, matcher.start(0)) + correzione + processExpression.substring(matcher.start(0) + matcher.group(0).length(), processExpression.length());
+				matcher = pattern.matcher(processExpression);
+			}
+
+			processExpression = processExpression.replace("⑴", MathematicalSymbols.POWER);
+
 			// Aggiungi i segni * accanto alle parentesi
 			pattern = Pattern.compile("\\([^\\(]+?\\)");
 			matcher = pattern.matcher(processExpression);
-			symbolsChanged = false;
 			while (matcher.find()) {
 				symbolsChanged = true;
 				// sistema i segni * impliciti prima e dopo l'espressione.
@@ -185,7 +213,7 @@ public class Expression extends FunctionMultipleValues {
 			debugSpaces += "  ";
 
 			// Convert the expression to a list of objects
-			Expression imputRawParenthesis = new Expression();
+			Expression imputRawParenthesis = new Expression(this);
 			imputRawParenthesis.setVariables(new Function[] {});
 			String tmp = "";
 			final String[] functions = concat(concat(concat(concat(MathematicalSymbols.functions(), MathematicalSymbols.parentheses()), MathematicalSymbols.signums(true, true)), MathematicalSymbols.variables()), MathematicalSymbols.genericSyntax());
@@ -199,28 +227,34 @@ public class Expression extends FunctionMultipleValues {
 					Function f = null;
 					switch (charI) {
 						case MathematicalSymbols.SUM:
-							f = new Sum(null, null);
+							f = new Sum(this, null, null);
 							break;
 						case MathematicalSymbols.SUM_SUBTRACTION:
-							f = new SumSubtraction(null, null);
+							f = new SumSubtraction(this, null, null);
+							break;
+						case MathematicalSymbols.SUBTRACTION:
+							f = new Subtraction(this, null, null);
+							break;
+						case MathematicalSymbols.MINUS:
+							f = new Negative(this, null);
 							break;
 						case MathematicalSymbols.MULTIPLICATION:
-							f = new Multiplication(null, null);
+							f = new Multiplication(this, null, null);
 							break;
 						case MathematicalSymbols.PRIORITARY_MULTIPLICATION:
-							f = new PrioritaryMultiplication(null, null);
+							f = new PrioritaryMultiplication(this, null, null);
 							break;
 						case MathematicalSymbols.DIVISION:
-							f = new Division(null, null);
+							f = new Division(this, null, null);
 							break;
 						case MathematicalSymbols.NTH_ROOT:
-							f = new Root(null, null);
+							f = new Root(this, null, null);
 							break;
 						case MathematicalSymbols.SQUARE_ROOT:
-							f = new RootSquare(null);
+							f = new RootSquare(this, null);
 							break;
 						case MathematicalSymbols.POWER:
-							f = new Power(null, null);
+							f = new Power(this, null, null);
 							break;
 						case MathematicalSymbols.PARENTHESIS_OPEN:
 							// Find the last closed parenthesis
@@ -253,7 +287,7 @@ public class Expression extends FunctionMultipleValues {
 								tmpExpr += processExpression.charAt(i);
 								i++;
 							}
-							f = new Expression(tmpExpr, debugSpaces, false);
+							f = new Expression(this, tmpExpr, debugSpaces, false);
 							break;
 						default:
 							if (Utils.isInArray(charI, MathematicalSymbols.variables())) {
@@ -265,7 +299,7 @@ public class Expression extends FunctionMultipleValues {
 								newVariableList.add(var1);
 								iy = new Variables(newVariableList.toArray(new Variable[newVariableList.size()]));
 								na = na.setVariableY(iy);
-								f = new Number(na);
+								f = new Number(this, na);
 							} else {
 								throw new java.lang.RuntimeException("Il carattere " + charI + " non è tra le funzioni designate!\nAggiungerlo ad esse o rimuovere il carattere dall'espressione!");
 							}
@@ -275,31 +309,37 @@ public class Expression extends FunctionMultipleValues {
 					} else if (f instanceof Number) {
 						if (imputRawParenthesis.getVariablesLength() == 0) {
 							if (tmp.length() > 0) {
-								imputRawParenthesis.addVariableToEnd(new Number(tmp));
+								imputRawParenthesis.addVariableToEnd(new Number(this, tmp));
 								Utils.debug.println(debugSpaces + "•Added value to expression:" + tmp);
-								imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(null, null));
+								imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(this, null, null));
-								Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(null, null).getSymbol());
+								Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(this, null, null).getSymbol());
 							}
 						} else {
 							if (tmp.length() > 0) {
 								if (imputRawParenthesis.getVariable(imputRawParenthesis.getVariablesLength() - 1) instanceof Number) {
-									imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(null, null));
+									imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(this, null, null));
-									Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(null, null).getSymbol());
+									Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(this, null, null).getSymbol());
 								}
 								if (tmp.equals("-")) {
-									tmp = "-1";
+									imputRawParenthesis.addVariableToEnd(new Subtraction(this, null, null));
+								} else {
+									imputRawParenthesis.addVariableToEnd(new Number(this, tmp));
+									Utils.debug.println(debugSpaces + "•Added value to expression:" + tmp);
 								}
-								imputRawParenthesis.addVariableToEnd(new Number(tmp));
-								Utils.debug.println(debugSpaces + "•Added value to expression:" + tmp);
 							}
 							if (tmp.length() > 0 || imputRawParenthesis.getVariable(imputRawParenthesis.getVariablesLength() - 1) instanceof Number) {
-								imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(null, null));
+								imputRawParenthesis.addVariableToEnd(new PrioritaryMultiplication(this, null, null));
-								Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(null, null).getSymbol());
+								Utils.debug.println(debugSpaces + "•Added variable to expression:" + new PrioritaryMultiplication(this, null, null).getSymbol());
 							}
 						}
 					} else {
 						if (tmp.length() != 0) {
-							imputRawParenthesis.addVariableToEnd(new Number(tmp));
+							if (tmp.equals("-")) {
+								if (tmp.equals("-")) {
+									tmp = "-1";
+								}
+							}
+							imputRawParenthesis.addVariableToEnd(new Number(this, tmp));
 							Utils.debug.println(debugSpaces + "•Added variable to expression:" + tmp);
 						}
 					}
@@ -322,7 +362,7 @@ public class Expression extends FunctionMultipleValues {
 			if (tmp.length() > 0) {
 				Utils.debug.println(debugSpaces + "•Added variable to expression:" + tmp);
 				try {
-					imputRawParenthesis.addVariableToEnd(new Number(tmp));
+					imputRawParenthesis.addVariableToEnd(new Number(this, tmp));
 				} catch (NumberFormatException ex) {
 					throw new Error(Errors.SYNTAX_ERROR);
 				}
@@ -366,7 +406,7 @@ public class Expression extends FunctionMultipleValues {
 							oldFunctionsArray[i-1] = null;
 							oldFunctionsList.remove(oldFunctionsList.size()-1);
 							i -= 1;
-							funzione = new RootSquare(null);
+							funzione = new RootSquare(this, null);
 						}
 					}
 					//Aggiunta della funzione alla lista grezza
@@ -399,7 +439,7 @@ public class Expression extends FunctionMultipleValues {
 						System.out.println("WARN: ---> POSSIBILE ERRORE????? <---");// BOH
 //						throw new Errore(Errori.SYNTAX_ERROR);
 						while (oldFunctionsList.size() > 1) {
-							oldFunctionsList.set(0, new Multiplication(oldFunctionsList.get(0), oldFunctionsList.remove(1)));
+							oldFunctionsList.set(0, new Multiplication(this, oldFunctionsList.get(0), oldFunctionsList.remove(1)));
 						}
 					}
 					Utils.debug.println(debugSpaces + "  •Phase: "+step);
@@ -408,7 +448,7 @@ public class Expression extends FunctionMultipleValues {
 						if (funzioneTMP instanceof FunctionTwoValues) {
 							if (step != "SN Functions") {
 								if (
-										(step == "sums" && (funzioneTMP instanceof Sum || funzioneTMP instanceof SumSubtraction) == true && ((funzioneTMP instanceof AnteriorFunction && ((AnteriorFunction) funzioneTMP).variable == null) || (funzioneTMP instanceof FunctionTwoValues && ((FunctionTwoValues) funzioneTMP).variable1 == null && ((FunctionTwoValues) funzioneTMP).variable2 == null) || (!(funzioneTMP instanceof AnteriorFunction) && !(funzioneTMP instanceof FunctionTwoValues))))
+										(step == "sums" && (funzioneTMP instanceof Sum || funzioneTMP instanceof SumSubtraction || funzioneTMP instanceof Subtraction) == true && ((funzioneTMP instanceof AnteriorFunction && ((AnteriorFunction) funzioneTMP).variable == null) || (funzioneTMP instanceof FunctionTwoValues && ((FunctionTwoValues) funzioneTMP).variable1 == null && ((FunctionTwoValues) funzioneTMP).variable2 == null) || (!(funzioneTMP instanceof AnteriorFunction) && !(funzioneTMP instanceof FunctionTwoValues))))
 										||
 										(
 											step.equals("prioritary multiplications")
@@ -441,6 +481,8 @@ public class Expression extends FunctionMultipleValues {
 											&&
 											(funzioneTMP instanceof SumSubtraction) == false
 											&&
+											(funzioneTMP instanceof Subtraction) == false
+											&&
 											(funzioneTMP instanceof Multiplication) == false
 											&&
 											(funzioneTMP instanceof PrioritaryMultiplication) == false
@@ -580,7 +622,7 @@ public class Expression extends FunctionMultipleValues {
 					if (f instanceof Number) {
 						ret.add(f);
 					} else {
-						ret.add(new Expression(new Function[]{(Function) f}));
+						ret.add(new Expression(this, new Function[]{(Function) f}));
 					}
 				}
 				return ret;
@@ -590,7 +632,7 @@ public class Expression extends FunctionMultipleValues {
 				if (f.isSolved() == false) {
 					List<Function> partial = f.solveOneStep();
 					for (Function fnc : partial) {
-						ret.add(new Expression(new Function[]{(Function) fnc}));
+						ret.add(new Expression(this, new Function[]{(Function) fnc}));
 					}
 				}
 			}
@@ -612,12 +654,18 @@ public class Expression extends FunctionMultipleValues {
 	
 	public boolean parenthesesNeeded() {
 		boolean parenthesesneeded = true;
-		if (initialParenthesis) {
+		if (initialParenthesis | parent instanceof Division) {
 			parenthesesneeded = false;
 		} else {
 			if (variables.length == 1) {
 				if (variables[0] instanceof Division) {
 					parenthesesneeded = false;
+				} else if (variables[0] instanceof Power) {
+					if (((Power)variables[0]).getVariable1() instanceof Number && ((Number)((Power)variables[0]).getVariable1()).soloIncognitaSemplice()) {
+						parenthesesneeded = false;
+					} else {
+						parenthesesneeded = true;
+					}
 				} else {
 					parenthesesneeded = true;
 				}

src/org/warp/picalculator/math/functions/Function.java

@@ -21,6 +21,10 @@ public interface Function {
 
 	public int getLine();
 	
+	public Function setParent(Function parent);
+	
+	public Function getParent();
+	
 	public void setSmall(boolean small);
 	
 	@Override

src/org/warp/picalculator/math/functions/FunctionMultipleValues.java

@@ -8,14 +8,17 @@ import org.warp.picalculator.Error;
 import com.rits.cloning.Cloner;
 
 public abstract class FunctionMultipleValues implements Function {
-	public FunctionMultipleValues() {
+	public FunctionMultipleValues(Function parent) {
+		setParent(parent);
 		setVariables(new Function[] {});
 	}
 
-	public FunctionMultipleValues(Function[] values) {
+	public FunctionMultipleValues(Function parent, Function[] values) {
+		setParent(parent);
 		setVariables(values);
 	}
 
+	protected Function parent;
 	protected Function[] variables;
 	protected int width;
 	protected int height;
@@ -27,6 +30,9 @@ public abstract class FunctionMultipleValues implements Function {
 	}
 
 	public void setVariables(Function[] value) {
+		for (Function f : value) {
+			f.setParent(this);
+		}
 		variables = value;
 	}
 
@@ -35,6 +41,7 @@ public abstract class FunctionMultipleValues implements Function {
 		Function[] tmp = new Function[vsize];
 		for (int i = 0; i < vsize; i++) {
 			tmp[i] = value.get(i);
+			tmp[i].setParent(this);
 		}
 		variables = tmp;
 	}
@@ -44,10 +51,12 @@ public abstract class FunctionMultipleValues implements Function {
 	}
 
 	public void setVariable(int index, Function value) {
+		value.setParent(this);
 		variables[index] = value;
 	}
 
 	public void addVariableToEnd(Function value) {
+		value.setParent(this);
 		int index = variables.length;
 		setVariablesLength(index + 1);
 		variables[index] = value;
@@ -76,6 +85,16 @@ public abstract class FunctionMultipleValues implements Function {
 	
 	protected abstract boolean isSolvable() throws Error;
 
+
+	public Function setParent(Function value) {
+		parent = value;
+		return this;
+	}
+	
+	public Function getParent() {
+		return parent;
+	}
+	
 	@Override
 	public abstract void generateGraphics();
 	

src/org/warp/picalculator/math/functions/FunctionTwoValues.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 
 import java.util.List;
@@ -14,12 +14,16 @@ import org.warp.picalculator.device.graphicengine.Display;
 import com.rits.cloning.Cloner;
 
 public abstract class FunctionTwoValues implements Function {
-	public FunctionTwoValues(Function value1, Function value2) {
+	public FunctionTwoValues(Function parent, Function value1, Function value2) {
-		setVariable1(value1);
+		this.parent = parent;
-		setVariable2(value2);
+		variable1 = value1;
+		variable2 = value2;
 	}
 
-	protected Function variable1 = (Function) new Number(Rational.ZERO);
+	protected Function parent;
+	
+	protected Function variable1 = (Function) new Number(null, Rational.ZERO);
+	protected Function variable2 = (Function) new Number(null, Rational.ZERO);
 	protected int width;
 	protected int height;
 	protected int line;
@@ -30,16 +34,25 @@ public abstract class FunctionTwoValues implements Function {
 	}
 
 	public void setVariable1(Function value) {
+		value.setParent(this);
 		variable1 = value;
 	}
 
-	protected Function variable2 = (Function) new Number(Rational.ZERO);
+	public Function getParent() {
+		return parent;
+	}
+
+	public Function setParent(Function value) {
+		parent = value;
+		return this;
+	}
 
 	public Function getVariable2() {
 		return variable2;
 	}
 
 	public void setVariable2(Function value) {
+		value.setParent(this);
 		variable2 = value;
 	}
 
@@ -76,9 +89,9 @@ public abstract class FunctionTwoValues implements Function {
 		variable1.draw(dx + x, ln - variable1.getLine() + y);
 		dx += 1+variable1.getWidth();
 		if (drawSignum()) {
-			Display.Render.setFont(Utils.getFont(small));
+			Display.Render.glSetFont(Utils.getFont(small));
 			glDrawStringLeft(dx + x, ln - Utils.getFontHeight(small) / 2 + y, getSymbol());
-			dx += getStringWidth(getSymbol());
+			dx += glGetStringWidth(getSymbol());
 		}
 		variable2.draw(dx + x, ln - variable2.getLine() + y);
 	}
@@ -124,7 +137,7 @@ public abstract class FunctionTwoValues implements Function {
 	}	
 
 	protected int calcWidth() {
-		return variable1.getWidth() + 1 + (drawSignum() ? getStringWidth(getSymbol()) : 0) + variable2.getWidth();
+		return variable1.getWidth() + 1 + (drawSignum() ? glGetStringWidth(getSymbol()) : 0) + variable2.getWidth();
 	}
 	
 	protected int calcHeight() {

src/org/warp/picalculator/math/functions/Joke.java

@@ -0,0 +1,93 @@
+package org.warp.picalculator.math.functions;
+
+import java.util.List;
+
+import org.warp.picalculator.Error;
+import org.warp.picalculator.Utils;
+import org.warp.picalculator.device.PIDisplay;
+import org.warp.picalculator.device.graphicengine.Display;
+import org.warp.picalculator.device.graphicengine.RAWFont;
+
+public class Joke implements Function {
+
+	public static final byte FISH = 0;
+	public static final byte TORNADO = 1;
+	public static final byte SHARKNADO = 2;
+	private static final String[] jokes =  new String[]{"♓", "TORNADO", "SHARKNADO"};
+	private static final int[] jokesFont =  new int[]{4, -1, -1};
+	private final byte joke;
+	
+	public Joke(byte joke) {
+		this.joke = joke;
+	}
+	
+	@Override
+	public String getSymbol() {
+		return "joke";
+	}
+
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		return null;
+	}
+
+	@Override
+	public boolean isSolved() throws Error {
+		return true;
+	}
+
+	@Override
+	public void generateGraphics() {
+		
+	}
+
+	@Override
+	public void draw(int x, int y) {
+		RAWFont rf = Display.Render.currentFont;
+		if (jokesFont[joke] >= 0) {
+			Display.Render.glSetFont(PIDisplay.fonts[jokesFont[joke]]);
+		}
+		Display.Render.glDrawStringLeft(x, y, jokes[joke]);
+		if (jokesFont[joke] >= 0) {
+			Display.Render.glSetFont(rf);
+		}
+	}
+
+	@Override
+	public int getWidth() {
+		if (jokesFont[joke] >= 0) {
+			return Display.Render.glGetStringWidth(PIDisplay.fonts[jokesFont[joke]], jokes[joke]);
+		} else {
+			return Display.Render.glGetStringWidth(jokes[joke]);
+		}
+	}
+
+	@Override
+	public int getHeight() {
+		if (jokesFont[joke] >= 0) {
+			return PIDisplay.fonts[jokesFont[joke]].charH;
+		} else {
+			return Display.Render.glGetCurrentFontHeight();
+		}
+	}
+
+	@Override
+	public int getLine() {
+		return getHeight()/2;
+	}
+	
+	@Override
+	public Function setParent(Function value) {
+		return this;
+	}
+
+	@Override
+	public Function getParent() {
+		return null;
+	}
+
+	@Override
+	public void setSmall(boolean small) {
+	}
+
+}

src/org/warp/picalculator/math/functions/Multiplication.java

@@ -9,11 +9,13 @@ import org.warp.picalculator.Errors;
 import org.warp.picalculator.Utils;
 import org.warp.picalculator.math.MathematicalSymbols;
 import org.warp.picalculator.math.Variable;
+import org.warp.picalculator.math.rules.NumberRule1;
+import org.warp.picalculator.math.rules.NumberRule2;
 
 public class Multiplication extends FunctionTwoValues {
 
-	public Multiplication(Function value1, Function value2) {
+	public Multiplication(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -26,13 +28,19 @@ public class Multiplication extends FunctionTwoValues {
 		if (variable1 instanceof Number & variable2 instanceof Number) {
 			return true;
 		}
+		if (NumberRule1.compare(this)) return true;
+		if (NumberRule2.compare(this)) return true;
 		return false;
 	}
 
 	@Override
 	public List<Function> solveOneStep() throws Error {
-		ArrayList<Function> result = new ArrayList<>();
+		List<Function> result = new ArrayList<>();
-		if (variable1.isSolved() & variable2.isSolved()) {
+		if (NumberRule1.compare(this)) {
+			result = NumberRule1.execute(this);
+		} else if (NumberRule2.compare(this)) {
+			result = NumberRule2.execute(this);
+		} else if (variable1.isSolved() & variable2.isSolved()) {
 			result.add(((Number)variable1).multiply((Number)variable2));
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
@@ -51,7 +59,7 @@ public class Multiplication extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Multiplication(f[0], f[1]));
+				result.add(new Multiplication(this.parent, f[0], f[1]));
 			}
 		}
 		return result;
@@ -93,9 +101,19 @@ public class Multiplication extends FunctionTwoValues {
 				} else if (tmpVar[val] instanceof Power) {
 					tmpVar[val] = ((Power) tmpVar[val]).variable1;
 				} else if (tmpVar[val] instanceof Root) {
+					if (val == 0) {
+						break;
+					}
 					ok[val] = true;
 				} else if (tmpVar[val] instanceof RootSquare) {
+					if (val == 0) {
+						break;
+					}
 					ok[val] = true;
+				} else if (tmpVar[val] instanceof Undefined) {
+					break;
+				} else if (tmpVar[val] instanceof Joke) {
+					break;
 				} else if (tmpVar[val] instanceof Expression) {
 					ok[0] = true;
 					ok[1] = true;

src/org/warp/picalculator/math/functions/Negative.java

@@ -0,0 +1,96 @@
+package org.warp.picalculator.math.functions;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.nevec.rjm.NumeroAvanzatoVec;
+import org.nevec.rjm.Rational;
+import org.warp.picalculator.Error;
+import org.warp.picalculator.Errors;
+import org.warp.picalculator.Utils;
+import org.warp.picalculator.device.graphicengine.Display;
+import org.warp.picalculator.math.MathematicalSymbols;
+import org.warp.picalculator.math.rules.NumberRule1;
+import org.warp.picalculator.math.rules.ExpandRule1;
+import org.warp.picalculator.math.rules.ExpandRule5;
+
+public class Negative extends AnteriorFunction {
+
+	public Negative(Function parent, Function value) {
+		super(parent, value);
+	}
+
+	@Override
+	public String getSymbol() {
+		return MathematicalSymbols.MINUS;
+	}
+	
+	@Override
+	public void generateGraphics() {
+		variable.setSmall(small);
+		variable.generateGraphics();
+		
+		height = getVariable().getHeight();
+		width = Display.Render.glGetStringWidth("-") + getVariable().getWidth();
+		line = getVariable().getLine();
+	}
+
+	@Override
+	protected boolean isSolvable() throws Error {
+		if (variable instanceof Number) return true;
+		if (ExpandRule1.compare(this)) return true;
+		if (ExpandRule5.compare(this)) return true;
+		return false;
+	}
+	
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		if (variable == null) {
+			throw new Error(Errors.SYNTAX_ERROR);
+		}
+		ArrayList<Function> result = new ArrayList<>();
+		if (ExpandRule1.compare(this)) {
+			result = ExpandRule1.execute(this);
+		} else if (ExpandRule5.compare(this)) {
+			result = ExpandRule5.execute(this);
+		} else if (variable.isSolved()) {
+			try {
+				Number var = (Number) getVariable();
+				result.add(var.multiply(new Number(null, "-1")));
+			} catch(NullPointerException ex) {
+				throw new Error(Errors.ERROR);
+			} catch(NumberFormatException ex) {
+				throw new Error(Errors.SYNTAX_ERROR);
+			} catch(ArithmeticException ex) {
+				throw new Error(Errors.NUMBER_TOO_SMALL);
+			}
+		} else {
+			List<Function> l1 = new ArrayList<Function>();
+			if (variable.isSolved()) {
+				l1.add(variable);
+			} else {
+				l1.addAll(variable.solveOneStep());
+			}
+			
+			for (Function f : l1) {
+				result.add(new Negative(this.parent, (Function)f));
+			}
+		}
+		return result;
+	}
+
+	@Override
+	public int getWidth() {
+		return width;
+	}
+
+	@Override
+	public int getHeight() {
+		return height;
+	}
+
+	@Override
+	public int getLine() {
+		return line;
+	}
+}

src/org/warp/picalculator/math/functions/Number.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glColor3f;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glFillRect;
@@ -25,33 +25,40 @@ import com.rits.cloning.Cloner;
 
 public class Number implements Function {
 
+	private Function parent;
 	protected NumeroAvanzatoVec term = NumeroAvanzatoVec.ZERO;
 	protected int width;
 	protected int height;
 	protected int line;
 	protected boolean small;
 
-	public Number(NumeroAvanzatoVec val) {
+	public Number(Function parent, NumeroAvanzatoVec val) {
+		this.parent = parent;
 		term = val;
 	}
 
-	public Number(String s) throws Error {
+	public Number(Function parent, String s) throws Error {
+		this.parent = parent;
 		term = new NumeroAvanzatoVec(new NumeroAvanzato(Utils.getRational(s), Rational.ONE));
 	}
 
-	public Number(Rational r) {
+	public Number(Function parent, Rational r) {
+		this.parent = parent;
 		term = new NumeroAvanzatoVec(new NumeroAvanzato(r, Rational.ONE));
 	}
 
-	public Number(BigInteger r) {
+	public Number(Function parent, BigInteger r) {
+		this.parent = parent;
 		term = new NumeroAvanzatoVec(new NumeroAvanzato(new Rational(r, BigInteger.ONE), Rational.ONE));
 	}
 
-	public Number(BigDecimal r) {
+	public Number(Function parent, BigDecimal r) {
+		this.parent = parent;
 		term = new NumeroAvanzatoVec(new NumeroAvanzato(Utils.getRational(r), Rational.ONE));
 	}
 
-	public Number(NumeroAvanzato numeroAvanzato) {
+	public Number(Function parent, NumeroAvanzato numeroAvanzato) {
+		this.parent = parent;
 		term = new NumeroAvanzatoVec(numeroAvanzato);
 	}
 
@@ -76,25 +83,25 @@ public class Number implements Function {
 	}
 
 	public Number add(Number f) throws Error {
-		Number ret = new Number(getTerm().add(f.getTerm()));
+		Number ret = new Number(this.parent, getTerm().add(f.getTerm()));
 		return ret;
 	}
 
 	public Number multiply(Number f) throws Error {
-		Number ret = new Number(getTerm().multiply(f.getTerm()));
+		Number ret = new Number(this.parent, getTerm().multiply(f.getTerm()));
 		return ret;
 	}
 
 	public Number divide(Number f) throws Error {
-		Number ret = new Number(getTerm().divide(f.getTerm()));
+		Number ret = new Number(this.parent, getTerm().divide(f.getTerm()));
 		return ret;
 	}
 
 	public Number pow(Number f) throws Error {
-		Number ret = new Number(NumeroAvanzatoVec.ONE);
+		Number ret = new Number(this.parent, NumeroAvanzatoVec.ONE);
 		if (f.getTerm().isBigInteger(true)) {
 			for (BigInteger i = BigInteger.ZERO; i.compareTo(f.getTerm().toBigInteger(true)) < 0; i = i.add(BigInteger.ONE)) {
-				ret = ret.multiply(new Number(getTerm()));
+				ret = ret.multiply(new Number(this.parent, getTerm()));
 			}
 		} else if (getTerm().isRational(true) && f.getTerm().isRational(false) && f.getTerm().toRational(false).compareTo(Rational.HALF) == 0) {
 			// Rational originalExponent = f.getTerm().toRational();
@@ -105,9 +112,9 @@ public class Number implements Function {
 			na = na.setVariableX(getTerm().toNumeroAvanzato().getVariableY().multiply(getTerm().toNumeroAvanzato().getVariableZ()));
 			na = na.setVariableY(new Variables());
 			na = na.setVariableZ(getTerm().toNumeroAvanzato().getVariableZ());
-			ret = new Number(na);
+			ret = new Number(this.parent, na);
 		} else {
-			ret = new Number(BigDecimalMath.pow(getTerm().BigDecimalValue(new MathContext(Utils.scale, Utils.scaleMode2)), f.getTerm().BigDecimalValue(new MathContext(Utils.scale, Utils.scaleMode2))));
+			ret = new Number(this.parent, BigDecimalMath.pow(getTerm().BigDecimalValue(new MathContext(Utils.scale, Utils.scaleMode2)), f.getTerm().BigDecimalValue(new MathContext(Utils.scale, Utils.scaleMode2))));
 		}
 		return ret;
 	}
@@ -130,7 +137,7 @@ public class Number implements Function {
 	public void draw(int x, int y) {
 		
 		if (getTerm().isBigInteger(false)) {
-			Display.Render.setFont(Utils.getFont(small));
+			Display.Render.glSetFont(Utils.getFont(small));
 			String t = toString();
 
 			if (t.startsWith("-")) {
@@ -143,7 +150,7 @@ public class Number implements Function {
 			glDrawStringLeft(x+1, y, t);
 		} else if (getTerm().isRational(false)) {
 			small = true;
-			Display.Render.setFont(Utils.getFont(true));
+			Display.Render.glSetFont(Utils.getFont(true));
 			Rational r = getTerm().toRational(false);
 			boolean minus = false;
 			int minusw = 0;
@@ -153,9 +160,9 @@ public class Number implements Function {
 				minus = true;
 				numerator = numerator.substring(1);
 			}
-			int w1 = getStringWidth(numerator);
+			int w1 = glGetStringWidth(numerator);
 			int h1 = Utils.getFontHeight(small);
-			int w2 = getStringWidth(r.denom().toString());
+			int w2 = glGetStringWidth(r.denom().toString());
 			int maxw;
 			if (w1 > w2) {
 				maxw = 1 + w1 + 1;
@@ -164,7 +171,7 @@ public class Number implements Function {
 			}
 			if (minus) {
 				if (drawMinus) {
-					minusw = getStringWidth("-");
+					minusw = glGetStringWidth("-");
 					minush = Utils.getFontHeight(small);
 					maxw += minusw;
 					glDrawStringLeft(x, y + h1 + 1 + 1 - (minush / 2), "-");
@@ -176,7 +183,7 @@ public class Number implements Function {
 			glFillRect(x + minusw + 1, y + h1 + 1, maxw, 1);
 		} else if (getTerm().toFancyString().contains("/")) {
 			small = true;
-			Display.Render.setFont(Utils.getFont(true));
+			Display.Render.glSetFont(Utils.getFont(true));
 			String r = getTerm().toFancyString();
 			String numer = r.substring(0, r.lastIndexOf("/"));
 			String denom = r.substring(numer.length() + 1, r.length());
@@ -188,9 +195,9 @@ public class Number implements Function {
 				minus = true;
 				numer = numer.substring(1);
 			}
-			int w1 = getStringWidth(numer.toString());
+			int w1 = glGetStringWidth(numer.toString());
 			int h1 = Utils.getFontHeight(small);
-			int w2 = getStringWidth(denom.toString());
+			int w2 = glGetStringWidth(denom.toString());
 			int maxw;
 			if (w1 > w2) {
 				maxw = w1 + 2;
@@ -201,7 +208,7 @@ public class Number implements Function {
 			int minush = 0;
 			if (minus) {
 				if (drawMinus) {
-					minusw = getStringWidth("-") + 1;
+					minusw = glGetStringWidth("-") + 1;
 					minush = Utils.getFontHeight(small);
 					maxw += minusw;
 					glDrawStringLeft(x, y + h1 + 1 + 1 - (minush / 2), "-");
@@ -212,7 +219,7 @@ public class Number implements Function {
 			glColor3f(0, 0, 0);
 			glFillRect(x + minusw + 1, y + h1 + 1, maxw, 1);
 		} else {
-			Display.Render.setFont(Utils.getFont(small));
+			Display.Render.glSetFont(Utils.getFont(small));
 			String r = getTerm().toFancyString();
 
 			if (r.startsWith("-")) {
@@ -274,7 +281,7 @@ public class Number implements Function {
 					t = t.substring(1);
 				}
 			}
-			return getStringWidth(t)+1;
+			return glGetStringWidth(t)+1;
 		} else if (getTerm().isRational(false)) {
 			Rational r = getTerm().toRational(false);
 			boolean minus = false;
@@ -283,8 +290,8 @@ public class Number implements Function {
 				minus = true;
 				numerator = numerator.substring(1);
 			}
-			int w1 = getStringWidth(numerator);
+			int w1 = glGetStringWidth(numerator);
-			int w2 = getStringWidth(r.denom().toString());
+			int w2 = glGetStringWidth(r.denom().toString());
 			int maxw;
 			if (w1 > w2) {
 				maxw = 1 + w1 + 1;
@@ -293,7 +300,7 @@ public class Number implements Function {
 			}
 			if (minus) {
 				if (drawMinus) {
-					maxw += getStringWidth("-");
+					maxw += glGetStringWidth("-");
 				}
 			}
 			return maxw + 1;
@@ -309,8 +316,8 @@ public class Number implements Function {
 				minus = true;
 				numer = numer.substring(1);
 			}
-			int w1 = getStringWidth(numer.toString());
+			int w1 = glGetStringWidth(numer.toString());
-			int w2 = getStringWidth(denom.toString());
+			int w2 = glGetStringWidth(denom.toString());
 			int maxw;
 			if (w1 > w2) {
 				maxw = w1 + 1;
@@ -319,7 +326,7 @@ public class Number implements Function {
 			}
 			if (minus) {
 				if (drawMinus) {
-					maxw += getStringWidth("-");
+					maxw += glGetStringWidth("-");
 				}
 			}
 			return maxw + 2;
@@ -332,7 +339,7 @@ public class Number implements Function {
 					r = r.substring(1);
 				}
 			}
-			return getStringWidth(r.toString())+1;
+			return glGetStringWidth(r.toString())+1;
 		}
 	}
 
@@ -344,7 +351,7 @@ public class Number implements Function {
 		}
 		return false;
 	}
-
+	
 	@Override
 	public int getLine() {
 		return line;
@@ -397,7 +404,34 @@ public class Number implements Function {
 	
 	@Override
 	public boolean equals(Object o) {
-		return o != null && o.hashCode() == this.hashCode();
+		if (o != null & term != null) {
+			if (o instanceof Number) {
+				NumeroAvanzatoVec nav = ((Number) o).getTerm();
+				if (term.isBigInteger(true) & nav.isBigInteger(true)) {
+					boolean na1 = term.toBigInteger(true).compareTo(BigInteger.ZERO) == 0;
+					boolean na2 = nav.toBigInteger(true).compareTo(BigInteger.ZERO) == 0;
+					if (na1 == na2) {
+						if (na1 == true) {
+							return true;
+						}
+					} else {
+						return false;
+					}
+				}
+				return nav.compareTo(term) == 0;
+			}
+		}
+		return false;
+	}
+
+	public Function setParent(Function value) {
+		parent = value;
+		return this;
+	}
+
+	@Override
+	public Function getParent() {
+		return parent;
 	}
 
 	/*

src/org/warp/picalculator/math/functions/Power.java

@@ -7,11 +7,13 @@ import org.warp.picalculator.Error;
 import org.warp.picalculator.Errors;
 import org.warp.picalculator.Utils;
 import org.warp.picalculator.math.MathematicalSymbols;
+import org.warp.picalculator.math.rules.FractionsRule4;
+import org.warp.picalculator.math.rules.FractionsRule5;
 
 public class Power extends FunctionTwoValues {
 
-	public Power(Function value1, Function value2) {
+	public Power(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -22,8 +24,13 @@ public class Power extends FunctionTwoValues {
 	@Override
 	protected boolean isSolvable() throws Error {
 		if (variable1 instanceof Number & variable2 instanceof Number) {
+			if (((Number)variable2).getTerm().hasVariables()) {
+				return false;
+			}
 			return true;
 		}
+		if (FractionsRule4.compare(this)) return true;
+		if (FractionsRule5.compare(this)) return true;
 		return false;
 	}
 	
@@ -43,8 +50,12 @@ public class Power extends FunctionTwoValues {
 	@Override
 	public List<Function> solveOneStep() throws Error {
 		ArrayList<Function> result = new ArrayList<>();
-		if (variable1.isSolved() & variable2.isSolved()) {
+		if (variable1 instanceof Number & variable2 instanceof Number) {
 			result.add((Function) ((Number)variable1).pow((Number)variable2));
+		} else if (FractionsRule4.compare(this)) {
+			result.addAll(FractionsRule4.execute(this));
+		} else if (FractionsRule5.compare(this)) {
+			result.addAll(FractionsRule5.execute(this));
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
 			List<Function> l2 = new ArrayList<Function>();
@@ -62,7 +73,7 @@ public class Power extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Power((Function)f[0], (Function)f[1]));
+				result.add(new Power(this.parent, (Function)f[0], (Function)f[1]));
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/PrioritaryMultiplication.java

@@ -10,8 +10,8 @@ import org.warp.picalculator.math.MathematicalSymbols;
 
 public class PrioritaryMultiplication extends FunctionTwoValues {
 
-	public PrioritaryMultiplication(Function value1, Function value2) {
+	public PrioritaryMultiplication(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -52,7 +52,7 @@ public class PrioritaryMultiplication extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new PrioritaryMultiplication((Function)f[0], (Function)f[1]));
+				result.add(new PrioritaryMultiplication(this.parent, (Function)f[0], (Function)f[1]));
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/Root.java

@@ -13,8 +13,8 @@ import org.warp.picalculator.math.MathematicalSymbols;
 
 public class Root extends FunctionTwoValues {
 
-	public Root(Function value1, Function value2) {
+	public Root(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -38,7 +38,7 @@ public class Root extends FunctionTwoValues {
 	@Override
 	protected boolean isSolvable() throws Error {
 		if (variable1 instanceof Number & variable2 instanceof Number) {
-			if ((((Number)variable2).pow(new Number(NumeroAvanzatoVec.ONE).divide((Number) variable1)).getTerm().isBigInteger(true))) {
+			if ((((Number)variable2).pow(new Number(this.parent, NumeroAvanzatoVec.ONE).divide((Number) variable1)).getTerm().isBigInteger(true))) {
 				return true;
 			}
 		}
@@ -49,7 +49,7 @@ public class Root extends FunctionTwoValues {
 	public List<Function> solveOneStep() throws Error {
 		ArrayList<Function> result = new ArrayList<>();
 		if (variable1.isSolved() & variable2.isSolved()) {
-			Number exponent = new Number(NumeroAvanzatoVec.ONE);
+			Number exponent = new Number(this.parent, NumeroAvanzatoVec.ONE);
 			exponent = exponent.divide((Number) variable1);
 			result.add(((Number)variable2).pow(exponent));
 		} else {
@@ -69,7 +69,11 @@ public class Root extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Root((Function)f[0], (Function)f[1]));
+				if (f[0] instanceof Number && ((Number)f[0]).equals(new Number(null, "2"))) {
+					result.add(new RootSquare(this.parent, (Function)f[1]));
+				} else {
+					result.add(new Root(this.parent, (Function)f[0], (Function)f[1]));
+				}
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/RootSquare.java

@@ -12,8 +12,8 @@ import org.warp.picalculator.math.MathematicalSymbols;
 
 public class RootSquare extends AnteriorFunction {
 
-	public RootSquare(Function value) {
+	public RootSquare(Function parent, Function value) {
-		super(value);
+		super(parent, value);
 	}
 
 	@Override
@@ -34,7 +34,7 @@ public class RootSquare extends AnteriorFunction {
 	@Override
 	protected boolean isSolvable() throws Error {
 		if (variable instanceof Number) {
-			if ((((Number)variable).pow(new Number(new Rational(1, 2))).getTerm().isBigInteger(true))) {
+			if ((((Number)variable).pow(new Number(this.parent, new Rational(1, 2))).getTerm().isBigInteger(true))) {
 				return true;
 			}
 		}
@@ -50,7 +50,7 @@ public class RootSquare extends AnteriorFunction {
 		if (variable.isSolved()) {
 			try {
 				Number var = (Number) getVariable();
-				result.add(var.pow(new Number(new Rational(1, 2))));
+				result.add(var.pow(new Number(this.parent, new Rational(1, 2))));
 			} catch(NullPointerException ex) {
 				throw new Error(Errors.ERROR);
 			} catch(NumberFormatException ex) {
@@ -67,7 +67,7 @@ public class RootSquare extends AnteriorFunction {
 			}
 			
 			for (Function f : l1) {
-				result.add(new RootSquare((Function)f));
+				result.add(new RootSquare(this.parent, (Function)f));
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/Subtraction.java

@@ -14,8 +14,8 @@ import org.warp.picalculator.math.Variables;
 
 public class Subtraction extends FunctionTwoValues {
 
-	public Subtraction(Function value1, Function value2) {
+	public Subtraction(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -38,19 +38,7 @@ public class Subtraction extends FunctionTwoValues {
 		}
 		ArrayList<Function> result = new ArrayList<>();
 		if (variable1.isSolved() & variable2.isSolved()) {
-			if (((Number)variable1).term.isBigInteger(false) & ((Number)variable2).term.isBigInteger(false)) {
+			result.add(((Number)variable1).add(((Number)variable2).multiply(new Number(this.parent, "-1"))));
-				if (((Number)variable1).term.toBigInteger(false).compareTo(new BigInteger("2")) == 0 && ((Number)variable2).term.toBigInteger(false).compareTo(new BigInteger("2")) == 0) {
-					NumeroAvanzato na = NumeroAvanzato.ONE;
-					Variables iy = na.getVariableY();
-					List<Variable> newVariableList = iy.getVariablesList();
-					newVariableList.add(new Variable('♓', 1, 1));
-					iy = new Variables(newVariableList.toArray(new Variable[newVariableList.size()]));
-					na = na.setVariableY(iy);
-					result.add(new Number(na));
-					return result;
-				}
-			}
-			result.add(((Number)variable1).add((Number)variable2).multiply(new Number("-1")));
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
 			List<Function> l2 = new ArrayList<Function>();
@@ -68,7 +56,7 @@ public class Subtraction extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Sum((Function)f[0], (Function)f[1]));
+				result.add(new Subtraction(this.parent, (Function)f[0], (Function)f[1]));
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/Sum.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 
 import java.math.BigInteger;
@@ -19,8 +19,8 @@ import org.warp.picalculator.math.Variables;
 
 public class Sum extends FunctionTwoValues {
 
-	public Sum(Function value1, Function value2) {
+	public Sum(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -43,15 +43,15 @@ public class Sum extends FunctionTwoValues {
 		}
 		ArrayList<Function> result = new ArrayList<>();
 		if (variable1.isSolved() & variable2.isSolved()) {
-			if (((Number)variable1).term.isBigInteger(false) & ((Number)variable2).term.isBigInteger(false)) {
+			if ((parent == null || parent.getParent() == null) && ((Number)variable1).term.isBigInteger(false) & ((Number)variable2).term.isBigInteger(false)) {
 				if (((Number)variable1).term.toBigInteger(false).compareTo(new BigInteger("2")) == 0 && ((Number)variable2).term.toBigInteger(false).compareTo(new BigInteger("2")) == 0) {
-					NumeroAvanzato na = NumeroAvanzato.ONE;
+					result.add(new Joke(Joke.FISH));
-					Variables iy = na.getVariableY();
+					return result;
-					List<Variable> newVariableList = iy.getVariablesList();
+				} else if (((Number)variable1).term.toBigInteger(false).compareTo(new BigInteger("20")) == 0 && ((Number)variable2).term.toBigInteger(false).compareTo(new BigInteger("20")) == 0) {
-					newVariableList.add(new Variable('♓', 1, 1));
+					result.add(new Joke(Joke.TORNADO));
-					iy = new Variables(newVariableList.toArray(new Variable[newVariableList.size()]));
+					return result;
-					na = na.setVariableY(iy);
+				} else if (((Number)variable1).term.toBigInteger(false).compareTo(new BigInteger("29")) == 0 && ((Number)variable2).term.toBigInteger(false).compareTo(new BigInteger("29")) == 0) {
-					result.add(new Number(na));
+					result.add(new Joke(Joke.SHARKNADO));
 					return result;
 				}
 			}
@@ -73,7 +73,7 @@ public class Sum extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new Sum((Function)f[0], (Function)f[1]));
+				result.add(new Sum(this.parent, (Function)f[0], (Function)f[1]));
 			}
 		}
 		return result;
@@ -102,10 +102,10 @@ public class Sum extends FunctionTwoValues {
 		int dx = 0;
 		variable1.draw(dx + x, ln - variable1.getLine() + y);
 		dx += variable1.getWidth();
-		Display.Render.setFont(Utils.getFont(small));
+		Display.Render.glSetFont(Utils.getFont(small));
 		dx += 1;
 		glDrawStringLeft(dx + x, ln - Utils.getFontHeight(small) / 2 + y, getSymbol());
-		dx += getStringWidth(getSymbol());
+		dx += glGetStringWidth(getSymbol());
 		variable2.draw(dx + x, ln - variable2.getLine() + y);
 	}
 
@@ -119,7 +119,7 @@ public class Sum extends FunctionTwoValues {
 		int dx = 0;
 		dx += variable1.getWidth();
 		dx += 1;
-		dx += getStringWidth(getSymbol());
+		dx += glGetStringWidth(getSymbol());
 		return dx += variable2.getWidth();
 	}
 }

src/org/warp/picalculator/math/functions/SumSubtraction.java

@@ -1,6 +1,6 @@
 package org.warp.picalculator.math.functions;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getStringWidth;
+import static org.warp.picalculator.device.graphicengine.Display.Render.glGetStringWidth;
 import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
 
 import java.util.ArrayList;
@@ -15,8 +15,8 @@ import org.warp.picalculator.math.MathematicalSymbols;
 
 public class SumSubtraction extends FunctionTwoValues {
 
-	public SumSubtraction(Function value1, Function value2) {
+	public SumSubtraction(Function parent, Function value1, Function value2) {
-		super(value1, value2);
+		super(parent, value1, value2);
 	}
 
 	@Override
@@ -40,7 +40,7 @@ public class SumSubtraction extends FunctionTwoValues {
 		ArrayList<Function> result = new ArrayList<>();
 		if (variable1.isSolved() & variable2.isSolved()) {
 			result.add(((Number)variable1).add((Number)variable2));
-			result.add(((Number)variable1).add(((Number)variable2).multiply(new Number("-1"))));
+			result.add(((Number)variable1).add(((Number)variable2).multiply(new Number(this.parent, "-1"))));
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
 			List<Function> l2 = new ArrayList<Function>();
@@ -58,7 +58,7 @@ public class SumSubtraction extends FunctionTwoValues {
 			Function[][] results = Utils.joinFunctionsResults(l1, l2);
 			
 			for (Function[] f : results) {
-				result.add(new SumSubtraction(f[0], f[1]));
+				result.add(new SumSubtraction(this.parent, f[0], f[1]));
 			}
 		}
 		return result;
@@ -87,10 +87,10 @@ public class SumSubtraction extends FunctionTwoValues {
 		int dx = 0;
 		variable1.draw(dx + x, ln - variable1.getLine() + y);
 		dx += variable1.getWidth();
-		Display.Render.setFont(Utils.getFont(small));
+		Display.Render.glSetFont(Utils.getFont(small));
 		dx += 1;
 		glDrawStringLeft(dx + x, ln - Utils.getFontHeight(small) / 2 + y, getSymbol());
-		dx += getStringWidth(getSymbol());
+		dx += glGetStringWidth(getSymbol());
 		variable2.draw(dx + x, ln - variable2.getLine() + y);
 	}
 
@@ -104,7 +104,7 @@ public class SumSubtraction extends FunctionTwoValues {
 		int dx = 0;
 		dx += variable1.getWidth();
 		dx += 1;
-		dx += getStringWidth(getSymbol());
+		dx += glGetStringWidth(getSymbol());
 		return dx += variable2.getWidth();
 	}
 }

src/org/warp/picalculator/math/functions/Undefined.java

@@ -0,0 +1,78 @@
+package org.warp.picalculator.math.functions;
+
+import java.util.List;
+
+import org.warp.picalculator.Error;
+import org.warp.picalculator.Utils;
+import org.warp.picalculator.device.graphicengine.Display;
+
+public class Undefined implements Function {
+
+	public Undefined(Function parent) {
+		setParent(parent);
+	}
+
+	@Override
+	public String getSymbol() {
+		return "undefined";
+	}
+
+	@Override
+	public List<Function> solveOneStep() throws Error {
+		return null;
+	}
+
+	@Override
+	public boolean isSolved() throws Error {
+		return true;
+	}
+
+	private int width, height, line;
+	private Function parent;
+	private boolean small;
+	
+	@Override
+	public void generateGraphics() {
+		width = Display.Render.glGetStringWidth("UNDEFINED");
+		height = Utils.getFontHeight(small);
+		line = height/2;
+	}
+
+	@Override
+	public void draw(int x, int y) {
+		Display.Render.glSetFont(Utils.getFont(small));
+		Display.Render.glDrawStringLeft(x, y, "UNDEFINED");
+	}
+
+	@Override
+	public int getWidth() {
+		return width;
+	}
+
+	@Override
+	public int getHeight() {
+		return height;
+	}
+
+	@Override
+	public int getLine() {
+		return line;
+	}
+
+	@Override
+	public Function setParent(Function parent) {
+		this.parent = parent;
+		return this;
+	}
+
+	@Override
+	public Function getParent() {
+		return parent;
+	}
+
+	@Override
+	public void setSmall(boolean small) {
+		this.small = small;
+	}
+
+}

src/org/warp/picalculator/math/functions/equations/Equation.java

@@ -19,8 +19,8 @@ import com.rits.cloning.Cloner;
 
 public class Equation extends FunctionTwoValues {
 
-	public Equation(Function value1, Function value2) {
+	public Equation(Function parent, Function value1, Function value2) {
-		super(value1,value2);
+		super(parent, value1,value2);
 	}
 
 	@Override
@@ -46,7 +46,10 @@ public class Equation extends FunctionTwoValues {
 			if (((Number)variable2).getTerm().isBigInteger(false) && ((Number)variable2).getTerm().toBigInteger(false).compareTo(new BigInteger("0")) == 0) {
 				result.add(this);
 			} else {
-				result.add(new Equation(new Subtraction(variable1, variable2), new Number("0")));
+				Equation e = new Equation(this.parent, null, null);
+				e.setVariable1(new Subtraction(e, variable1, variable2));
+				e.setVariable2(new Number(e, "0"));
+				result.add(e);
 			}
 		} else {
 			List<Function> l1 = new ArrayList<Function>();
@@ -79,7 +82,7 @@ public class Equation extends FunctionTwoValues {
 				if (cur2 >= size1) cur2 = 0;
 			}
 			for (Function[] f : results) {
-				result.add(new Equation(f[0], f[1]));
+				result.add(new Equation(this.parent, f[0], f[1]));
 			}
 		}
 		return result;

src/org/warp/picalculator/math/functions/equations/EquationResult.java

@@ -6,7 +6,7 @@ import org.warp.picalculator.math.functions.Number;
 
 public class EquationResult {
 	public boolean isAnEquation = false;
-	public Number LR = new Number(new BigInteger("0"));
+	public Number LR = new Number(null, new BigInteger("0"));
 
 	public EquationResult(Number LR, boolean isAnEquation) {
 		this.LR = LR;

src/org/warp/picalculator/math/functions/equations/EquationsSystem.java

@@ -14,16 +14,16 @@ import org.warp.picalculator.math.functions.Number;
 public class EquationsSystem extends FunctionMultipleValues {
 	static final int spacing = 2;
 	
-	public EquationsSystem() {
+	public EquationsSystem(Function parent) {
-		super();
+		super(parent);
 	}
 	
-	public EquationsSystem(Function value) {
+	public EquationsSystem(Function parent, Function value) {
-		super(new Function[]{value});
+		super(parent, new Function[]{value});
 	}
 	
-	public EquationsSystem(Function[] value) {
+	public EquationsSystem(Function parent, Function[] value) {
-		super(value);
+		super(parent, value);
 	}
 
 	@Override
@@ -52,7 +52,7 @@ public class EquationsSystem extends FunctionMultipleValues {
 					if (f instanceof Number) {
 						ret.add(f);
 					} else {
-						ret.add(new Expression(new Function[]{(Function) f}));
+						ret.add(new Expression(this.parent, new Function[]{(Function) f}));
 					}
 				}
 				return ret;
@@ -62,7 +62,7 @@ public class EquationsSystem extends FunctionMultipleValues {
 				if (f.isSolved() == false) {
 					List<Function> partial = f.solveOneStep();
 					for (Function fnc : partial) {
-						ret.add(new Expression(new Function[]{(Function) fnc}));
+						ret.add(new Expression(this.parent, new Function[]{(Function) fnc}));
 					}
 				}
 			}

src/org/warp/picalculator/math/functions/equations/EquationsSystemPart.java

@@ -13,8 +13,8 @@ import org.warp.picalculator.math.functions.Function;
 
 public class EquationsSystemPart extends AnteriorFunction {
 
-	public EquationsSystemPart(Equation equazione) {
+	public EquationsSystemPart(Function parent, Equation equazione) {
-		super(equazione);
+		super(parent, equazione);
 	}
 
 	@Override

src/org/warp/picalculator/math/rules/ExpandRule1.java

@@ -0,0 +1,127 @@
+package org.warp.picalculator.math.rules;
+
+import java.util.ArrayList;
+
+import org.warp.picalculator.Error;
+import org.warp.picalculator.math.functions.Expression;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.FunctionTwoValues;
+import org.warp.picalculator.math.functions.Negative;
+import org.warp.picalculator.math.functions.Subtraction;
+import org.warp.picalculator.math.functions.Sum;
+import org.warp.picalculator.math.functions.SumSubtraction;
+
+/**
+ * Expand rule<br>
+ * <b>-(+a+b) = -a-b</b><br>
+ * <b>-(+a-b) = -a+b</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class ExpandRule1 {
+
+	public static boolean compare(Function f) {
+		if (f instanceof Negative) {
+			Negative fnc = (Negative) f;
+			if (fnc.getVariable() instanceof Expression) {
+				Expression expr = (Expression) fnc.getVariable();
+				if (expr.getVariablesLength() == 1) {
+					if (expr.getVariable(0) instanceof Sum) {
+						return true;
+					} else if (expr.getVariable(0) instanceof Subtraction) {
+						return true;
+					} else if (expr.getVariable(0) instanceof SumSubtraction) {
+						return true;
+					}
+				}
+			}
+		} else if (f instanceof Subtraction || f instanceof SumSubtraction) {
+			FunctionTwoValues fnc = (FunctionTwoValues) f;
+			if (fnc.getVariable2() instanceof Expression) {
+				Expression expr = (Expression) fnc.getVariable2();
+				if (expr.getVariablesLength() == 1) {
+					if (expr.getVariable(0) instanceof Sum) {
+						return true;
+					} else if (expr.getVariable(0) instanceof Subtraction) {
+						return true;
+					} else if (expr.getVariable(0) instanceof SumSubtraction) {
+						return true;
+					}
+				}
+			}
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		
+		Expression expr = null;
+		int fromSubtraction = 0;
+		FunctionTwoValues subtraction = null;
+		if (f instanceof Negative) {
+			expr = ((Expression)((Negative) f).getVariable());
+		} else if (f instanceof Subtraction || f instanceof SumSubtraction) {
+			expr = ((Expression)((FunctionTwoValues) f).getVariable2());
+			if (f instanceof Subtraction) {
+				fromSubtraction = 1;
+			} else {
+				fromSubtraction = 2;
+			}
+		}
+		
+		if (f instanceof SumSubtraction) {
+			
+		}
+
+		Function fnc = expr.getVariable(0);
+		if (fnc instanceof Sum) {
+			Function a = ((Sum) fnc).getVariable1();
+			Function b = ((Sum) fnc).getVariable2();
+			Subtraction fnc2 = new Subtraction(((Negative) f).getParent(), null, b);
+			fnc2.setVariable1(new Negative(fnc2, a));
+			if (fromSubtraction > 0) {
+				subtraction = new Subtraction(f.getParent(), null, null);
+				subtraction.setVariable1(((FunctionTwoValues)f).getVariable1());
+				subtraction.setVariable2(fnc2);
+				result.add(subtraction);
+			} else {
+				result.add(fnc2);
+			}
+		} else if (fnc instanceof Subtraction) {
+			Function a = ((Subtraction) fnc).getVariable1();
+			Function b = ((Subtraction) fnc).getVariable2();
+			Sum fnc2 = new Sum(((Negative) f).getParent(), null, b);
+			fnc2.setVariable1(new Negative(fnc2, a));
+			if (fromSubtraction > 0) {
+				subtraction = new Subtraction(f.getParent(), null, null);
+				subtraction.setVariable1(((FunctionTwoValues)f).getVariable1());
+				subtraction.setVariable2(fnc2);
+				result.add(subtraction);
+			} else {
+				result.add(fnc2);
+			}
+		} else if (fnc instanceof SumSubtraction) {
+			Function a = ((Subtraction) fnc).getVariable1();
+			Function b = ((Subtraction) fnc).getVariable2();
+			Sum fnc2 = new Sum(((Negative) f).getParent(), null, b);
+			fnc2.setVariable1(new Negative(fnc2, a));
+			Subtraction fnc3 = new Subtraction(((Negative) f).getParent(), null, b);
+			fnc3.setVariable1(new Negative(fnc2, a));
+			if (fromSubtraction > 0) {
+				subtraction = new SumSubtraction(f.getParent(), null, null);
+				subtraction.setVariable1(((FunctionTwoValues)f).getVariable1());
+				subtraction.setVariable2(fnc2);
+				result.add(subtraction);
+				subtraction = new SumSubtraction(f.getParent(), null, null);
+				subtraction.setVariable1(((FunctionTwoValues)f).getVariable1());
+				subtraction.setVariable2(fnc3);
+				result.add(subtraction);
+			} else {
+				result.add(fnc2);
+			}
+		}
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/ExpandRule5.java

@@ -0,0 +1,47 @@
+package org.warp.picalculator.math.rules;
+
+import java.util.ArrayList;
+
+import org.warp.picalculator.Error;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Negative;
+import org.warp.picalculator.math.functions.Subtraction;
+
+/**
+ * Expand rule<br>
+ * <b>-(-a) = a</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class ExpandRule5 {
+
+	public static boolean compare(Function f) {
+		if (f instanceof Negative) {
+			Negative fnc = (Negative) f;
+			if (fnc.getVariable() instanceof Negative) {
+				return true;
+			}
+		} else if (f instanceof Subtraction) {
+			Subtraction fnc = (Subtraction) f;
+			if (fnc.getVariable2() instanceof Negative) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Function a = null;
+
+		if (f instanceof Negative) {
+			Negative fnc = (Negative) f;
+			result.add(((Negative)fnc.getVariable()).getVariable().setParent(f.getParent()));
+		} else if (f instanceof Subtraction) {
+			Subtraction fnc = (Subtraction) f;
+			result.add(((Negative)fnc.getVariable2()).getVariable().setParent(f.getParent()));
+		}
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/FractionsRule1.java

@@ -0,0 +1,50 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Multiplication;
+import org.warp.picalculator.math.functions.Number;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Fractions rule<br>
+ * <b>0 / a = 0</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class FractionsRule1 {
+
+	public static boolean compare(Function f) {
+		try {
+			if (f instanceof Division) {
+				Division fnc = (Division) f;
+				if (fnc.getVariable1() instanceof Number) {
+					Number numb1 = (Number) fnc.getVariable1();
+					if (numb1.equals(new Number(null, "0"))) {
+						if (fnc.getVariable2() instanceof Number) {
+							Number numb2 = (Number) fnc.getVariable2();
+							if (numb2.equals(new Number(null, "0"))) {
+								return false;
+							}
+						}
+						return true;
+					}
+				}
+			}
+		} catch (Error e) {
+			e.printStackTrace();
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		result.add(new Number(f.getParent(), "0"));
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/FractionsRule2.java

@@ -0,0 +1,45 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Multiplication;
+import org.warp.picalculator.math.functions.Number;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Fractions rule<br>
+ * <b>a / 1 = a</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class FractionsRule2 {
+
+	public static boolean compare(Function f) {
+		try {
+			if (f instanceof Division) {
+				Division fnc = (Division) f;
+				if (fnc.getVariable2() instanceof Number) {
+					Number numb = (Number) fnc.getVariable2();
+					if (numb.equals(new Number(null, "1"))) {
+						return true;
+					}
+				}
+			}
+		} catch (Error e) {
+			e.printStackTrace();
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Division fnc = (Division) f;
+		result.add(fnc.getVariable1().setParent(f.getParent()));
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/FractionsRule3.java

@@ -0,0 +1,38 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Multiplication;
+import org.warp.picalculator.math.functions.Number;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Fractions rule<br>
+ * <b>a / 1 = a</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class FractionsRule3 {
+
+	public static boolean compare(Function f) {
+		if (f instanceof Division) {
+			Division fnc = (Division) f;
+			if (fnc.getVariable1().equals(fnc.getVariable2())) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Division fnc = (Division) f;
+		result.add(fnc.getVariable1().setParent(f.getParent()));
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/FractionsRule4.java

@@ -0,0 +1,45 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Number;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Power;
+
+import java.util.ArrayList;
+
+import org.nevec.rjm.NumeroAvanzato;
+import org.nevec.rjm.NumeroAvanzatoVec;
+import org.warp.picalculator.Error;
+
+/**
+ * Fractions rule<br>
+ * <b>(a / b) ^ -1 = b / a</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class FractionsRule4 {
+
+	public static boolean compare(Function f) throws Error {
+		if (f instanceof Power) {
+			Power fnc = (Power) f;
+			if (fnc.getVariable1() instanceof Division && fnc.getVariable2() instanceof Number) {
+				Number n2 = (Number) fnc.getVariable2();
+				if (n2.equals(new Number(null, "-1"))) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Power fnc = (Power) f;
+		Function a = ((Division)fnc.getVariable1()).getVariable1();
+		Function b = ((Division)fnc.getVariable1()).getVariable2();
+		Division res = new Division(f.getParent(), b, a);
+		result.add(res);
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/FractionsRule5.java

@@ -0,0 +1,49 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Number;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Power;
+
+import java.math.BigInteger;
+import java.util.ArrayList;
+
+import org.nevec.rjm.NumeroAvanzato;
+import org.nevec.rjm.NumeroAvanzatoVec;
+import org.warp.picalculator.Error;
+
+/**
+ * Fractions rule<br>
+ * <b>(a / b) ^ -c = (b / a) ^ c</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class FractionsRule5 {
+
+	public static boolean compare(Function f) throws Error {
+		if (f instanceof Power) {
+			Power fnc = (Power) f;
+			if (fnc.getVariable1() instanceof Division && fnc.getVariable2() instanceof Number) {
+				Number n2 = (Number) fnc.getVariable2();
+				if (n2.getTerm().compareTo(new NumeroAvanzatoVec(NumeroAvanzato.ZERO)) < 0) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Power fnc = (Power) f;
+		Function a = ((Division)fnc.getVariable1()).getVariable1();
+		Function b = ((Division)fnc.getVariable1()).getVariable2();
+		Function c = ((Number)fnc.getVariable2()).multiply(new Number(null, "-1"));
+		Division dv = new Division(null, b, a);
+		Power pow = new Power(f.getParent(), dv, c);
+		dv.setParent(pow);
+		result.add(pow);
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/NumberRule1.java

@@ -0,0 +1,49 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Multiplication;
+import org.warp.picalculator.math.functions.Number;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Number rule<br>
+ * <b>a * 0 = 0</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class NumberRule1 {
+
+	public static boolean compare(Function f) {
+		try {
+			if (f instanceof Multiplication) {
+				Multiplication mult = (Multiplication) f;
+				if (mult.getVariable1() instanceof Number) {
+					Number numb = (Number) mult.getVariable1();
+					if (numb.equals(new Number(null, "0"))) {
+						return true;
+					}
+				}
+				if (mult.getVariable2() instanceof Number) {
+					Number numb = (Number) mult.getVariable2();
+					if (numb.equals(new Number(null, "0"))) {
+						return true;
+					}
+				}
+			}
+		} catch (Error e) {
+			e.printStackTrace();
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		result.add(new Number(f.getParent(), "0"));
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/NumberRule2.java

@@ -0,0 +1,67 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Multiplication;
+import org.warp.picalculator.math.functions.Number;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Number rule<br>
+ * <b>a * 1 = a</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class NumberRule2 {
+
+	public static boolean compare(Function f) {
+		try {
+			if (f instanceof Multiplication) {
+				Multiplication mult = (Multiplication) f;
+				if (mult.getVariable1() instanceof Number) {
+					Number numb = (Number) mult.getVariable1();
+					if (numb.equals(new Number(null, "1"))) {
+						return true;
+					}
+				}
+				if (mult.getVariable2() instanceof Number) {
+					Number numb = (Number) mult.getVariable2();
+					if (numb.equals(new Number(null, "1"))) {
+						return true;
+					}
+				}
+			}
+		} catch (Error e) {
+			e.printStackTrace();
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		Function a = null;
+		boolean aFound = false;
+		Multiplication mult = (Multiplication) f;
+		if (aFound == false & mult.getVariable1() instanceof Number) {
+			Number numb = (Number) mult.getVariable1();
+			if (numb.equals(new Number(null, "1"))) {
+				a = mult.getVariable2();
+				aFound = true;
+			}
+		}
+		if (aFound == false && mult.getVariable2() instanceof Number) {
+			Number numb = (Number) mult.getVariable2();
+			if (numb.equals(new Number(null, "1"))) {
+				a = mult.getVariable1();
+				aFound = true;
+			}
+		}
+		
+		result.add(a.setParent(f.getParent()));
+		return result;
+	}
+
+}

src/org/warp/picalculator/math/rules/UndefinedRule2.java

@@ -0,0 +1,43 @@
+package org.warp.picalculator.math.rules;
+
+import org.warp.picalculator.math.functions.Division;
+import org.warp.picalculator.math.functions.Function;
+import org.warp.picalculator.math.functions.Number;
+import org.warp.picalculator.math.functions.Undefined;
+
+import java.util.ArrayList;
+
+import org.warp.picalculator.Error;
+
+/**
+ * Undefined rule<br>
+ * <b>a / 0 = undefined</b>
+ * @author Andrea Cavalli
+ *
+ */
+public class UndefinedRule2 {
+
+	public static boolean compare(Function f) {
+		try {
+			if (f instanceof Division) {
+				Division fnc = (Division) f;
+				if (fnc.getVariable2() instanceof Number) {
+					Number numb = (Number) fnc.getVariable2();
+					if (numb.equals(new Number(null, "0"))) {
+						return true;
+					}
+				}
+			}
+		} catch (Error e) {
+			e.printStackTrace();
+		}
+		return false;
+	}
+
+	public static ArrayList<Function> execute(Function f) throws Error {
+		ArrayList<Function> result = new ArrayList<>();
+		result.add(new Undefined(f.getParent()));
+		return result;
+	}
+
+}

src/org/warp/picalculator/screens/EquationScreen.java

@@ -18,6 +18,9 @@ import org.warp.picalculator.device.graphicengine.Screen;
 import org.warp.picalculator.math.Calculator;
 import org.warp.picalculator.math.functions.Function;
 
+import com.rits.cloning.Cloner;
+import com.rits.cloning.FastClonerArrayList;
+
 public class EquationScreen extends Screen {
 
 	public float endLoading;
@@ -28,6 +31,7 @@ public class EquationScreen extends Screen {
 	public volatile float showCaretDelta = 0f;
 	public List<Function> f;
 	public List<Function> f2;
+	public int resultsCount;
 	public int ew1;
 	public int ew2;
 	public int eh2;
@@ -84,8 +88,11 @@ public class EquationScreen extends Screen {
 		// Funzione f = new Parentesi("5Y+XY=2", "")
 
 //			calcola("((5^2+3√(100/0.1))+Ⓐ(7)+9/15*2√(26/2))/21");
-		f = new ArrayList<Function>();
+		if (f == null & f2 == null) {
-		f2 = new ArrayList<Function>();
+			f = new ArrayList<Function>();
+			f2 = new ArrayList<Function>();
+			resultsCount = 0;
+		}
 //			interpreta("{(5X*(15X/3X))+(25X/(5X*(15X/3X)))=15{X=5"); //TODO RIMUOVERE
 
 		// long start = System.nanoTime();
@@ -122,7 +129,7 @@ public class EquationScreen extends Screen {
 	}
 	
 	public void solve() throws Error {
-		Calculator.solve();
+		Calculator.solve(this);
 	}
 
 	@Override
@@ -137,14 +144,14 @@ public class EquationScreen extends Screen {
 
 	@Override
 	public void render() {
-		Display.Render.setFont(Utils.getFont(false));
+		Display.Render.glSetFont(Utils.getFont(false));
 		glClearColor(0xFFCCE7D4);
 		glColor3f(0, 0, 0);
 		glDrawStringLeft(2, 22, nuovaEquazione.substring(0, caretPos)+(showCaret?"|":"")+nuovaEquazione.substring(((showCaret==false||nuovaEquazione.length()<=caretPos)?caretPos:caretPos+1), nuovaEquazione.length()));
 		if (f != null) {
 			int topSpacing = 0;
 			for (Function f : f) {
-				f.draw(2, 22+1+getFontHeight()+1+topSpacing);
+				f.draw(2, 22+1+glGetCurrentFontHeight()+1+topSpacing);
 				topSpacing += f.getHeight() + 2;
 			}
 		}
@@ -154,6 +161,13 @@ public class EquationScreen extends Screen {
 				bottomSpacing += f.getHeight()+2;
 				f.draw(Display.getWidth() - 2 - f.getWidth(), Display.getHeight() - bottomSpacing);
 			}
+			if (resultsCount > 1 && resultsCount != f2.size()) {
+				String resultsCountText = resultsCount+" total results".toUpperCase();
+				glColor(0xFF9AAEA0);
+				glSetFont(Utils.getFont(true));
+				bottomSpacing += glGetCurrentFontHeight()+2;
+				glDrawStringRight(Display.getWidth() - 2, Display.getHeight() - bottomSpacing, resultsCountText);
+			}
 		}
 	}
 
@@ -172,7 +186,7 @@ public class EquationScreen extends Screen {
 		switch (k) {
 			case SIMPLIFY:
 				if (nuovaEquazione.length() > 0) {
-					Calculator.simplify();
+					Calculator.simplify(this);
 				}
 				return true;
 			case SOLVE:
@@ -184,6 +198,7 @@ public class EquationScreen extends Screen {
 					if (nuovaEquazione != equazioneCorrente && nuovaEquazione.length() > 0) {
 						try {
 							try {
+								changeEquationScreen();
 								interpreta(nuovaEquazione);
 								solve();
 							} catch (Exception ex) {
@@ -322,12 +337,24 @@ public class EquationScreen extends Screen {
 		}
 	}
 	
+	private void changeEquationScreen() {
+		if (equazioneCorrente != null && equazioneCorrente.length() > 0) {
+			EquationScreen cloned = clone();
+			cloned.caretPos = cloned.equazioneCorrente.length();
+			cloned.nuovaEquazione = cloned.equazioneCorrente;
+			PIDisplay.INSTANCE.replaceScreen(cloned);
+			this.initialized = false;
+			PIDisplay.INSTANCE.setScreen(this);
+			
+		}
+	}
+
 	public void typeChar(String chr) {
 		nuovaEquazione=nuovaEquazione.substring(0, caretPos)+chr+nuovaEquazione.substring(caretPos, nuovaEquazione.length());
 		caretPos+=1;
 		showCaret = true;
 		showCaretDelta = 0L;
-		f.clear();
+//		f.clear(); //TODO: I removed this line to prevent input blanking when pressing EQUALS button and cloning this screen, but I must see why I created this part of code.
 	}
 
 	@Override
@@ -335,5 +362,34 @@ public class EquationScreen extends Screen {
 		
 		return false;
 	}
+	
+	@Override
+	public EquationScreen clone() {
+		EquationScreen es = this;
+		EquationScreen es2 = new EquationScreen();
+		es2.endLoading = es.endLoading;
+		es2.nuovaEquazione = es.nuovaEquazione;
+		es2.equazioneCorrente = es.equazioneCorrente;
+		es2.showCaret = es.showCaret;
+		es2.showCaretDelta = es.showCaretDelta;
+		es2.caretPos = es.caretPos;
+		es2.f = Utils.cloner.deepClone(es.f);
+		es2.f2 = Utils.cloner.deepClone(es.f2);
+		es2.resultsCount = es.resultsCount;
+		es2.ew1 = es.ew1;
+		es2.ew2 = es.ew2;
+		es2.eh2 = es.eh2;
+		es2.x1 = es.x1;
+		es2.x2 = es.x2;
+		es2.requiresleep1 = es.requiresleep1;
+		es2.requiresleep2 = es.requiresleep2;
+		es2.autoscroll = es.autoscroll;
+		es2.errorLevel = es.errorLevel;
+		es2.err1 = es.err1;
+		es2.err2 = es.err2;
+		es2.mustRefresh = es.mustRefresh;
+		es2.aftersleep = es.aftersleep;
+		return es2;
+	}
 
 }

src/org/warp/picalculator/screens/LoadingScreen.java

@@ -69,7 +69,7 @@ public class LoadingScreen extends Screen {
 
 	@Override
 	public void render() {
-		setFont(fonts[2]);
+		glSetFont(fonts[2]);
 		colore(1.0f, 1.0f, 1.0f, 1.0f);
 		glDrawStringCenter((Main.screenSize[0] / 2) - 1,(int) ((Main.screenSize[1]/ 2) - 25 + loadingTextTranslation), "ANDREA CAVALLI'S CALCULATOR");
 		colore(1.0f, 1.0f, 1.0f, 1.0f);
@@ -81,9 +81,9 @@ public class LoadingScreen extends Screen {
 		colore(1.0f, 0.5f, 0.0f, 1.0f);
 		glDrawStringCenter((Main.screenSize[0] / 2), (int) ((Main.screenSize[1]/ 2) - 25 + loadingTextTranslation), "ANDREA CAVALLI'S CALCULATOR");
 		colore(0.0f, 0.0f, 0.0f, 0.75f);
-		setFont(fonts[0]);
+		glSetFont(fonts[0]);
 		glDrawStringCenter((Main.screenSize[0] / 2), (Main.screenSize[1]/ 2) + 11, "LOADING");
-		setFont(fonts[1]);
+		glSetFont(fonts[1]);
 		colore(0.0f, 0.0f, 0.0f, 0.5f);
 		glDrawStringCenter((Main.screenSize[0] / 2), (Main.screenSize[1]/ 2) + 22, "PLEASE WAIT...");
 	

src/org/warp/picalculator/screens/MarioScreen.java

@@ -1,10 +1,6 @@
 package org.warp.picalculator.screens;
 
-import static org.warp.picalculator.device.graphicengine.Display.Render.getMatrixOfImage;
+import static org.warp.picalculator.device.graphicengine.Display.Render.*;
-import static org.warp.picalculator.device.graphicengine.Display.Render.glClearColor;
-import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawSkin;
-import static org.warp.picalculator.device.graphicengine.Display.Render.glDrawStringLeft;
-import static org.warp.picalculator.device.graphicengine.Display.Render.setFont;
 
 import java.awt.image.BufferedImage;
 import java.io.IOException;
@@ -142,7 +138,7 @@ public class MarioScreen extends Screen {
 		if (errored) {
 			glDrawStringLeft(0, 20, "ERROR");
 		} else {
-			setFont(PIDisplay.fonts[0]);
+			glSetFont(PIDisplay.fonts[0]);
 			glClearColor(0xff9290ff);
 			glDrawSkin(groundSize[0], ground, 0, 25+25, 0, 0, 16, 16, false);
 			glDrawSkin(groundSize[0], ground, 16, 25+25, 0, 0, 16, 16, false);
@@ -163,6 +159,23 @@ public class MarioScreen extends Screen {
 			glDrawSkin(groundSize[0], ground, 16*7, 25+25+16, 0, 0, 16, 16, false);
 			glDrawSkin(groundSize[0], ground, 16*8, 25+25+16, 0, 0, 16, 16, false);
 			
+//		EASTER EGG
+//			glSetFont(PIDisplay.fonts[4]);
+//			glColor(0xFF000000);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "A");
+//			glColor(0xFF800000);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "B");
+//			glColor(0xFFeea28e);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "C");
+//			glColor(0xFFee7255);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "D");
+//			glColor(0xFFeac0b0);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "E");
+//			glColor(0xFFf3d8ce);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "F");
+//			glColor(0xffede7);
+//			glDrawStringRight(0, Main.screenSize[1]-glGetCurrentFontHeight(), "G");
+			
 			//DRAW MARIO
 			glDrawSkin(skinSize[0], skin, getPosX()-18, 25+getPosY(), 35*(marioSkinPos[0]+(flipped?2:1)), 27*marioSkinPos[1], 35*(marioSkinPos[0]+(flipped?1:2)), 27*(marioSkinPos[1]+1), true);
 		}