histogram: Implement AddAssign and MulAssign

Also clarify documentation and name of `min`/`max`.

src/histogram.rs

@@ -132,14 +132,18 @@ macro_rules! define_histogram {
             }
 
             /// Return the lower range limit.
+            ///
+            /// (The corresponding bin might be empty.)
             #[inline]
-            pub fn min(&self) -> f64 {
+            pub fn range_min(&self) -> f64 {
                 self.range[0]
             }
 
             /// Return the upper range limit.
+            ///
+            /// (The corresponding bin might be empty.)
             #[inline]
-            pub fn max(&self) -> f64 {
+            pub fn range_max(&self) -> f64 {
                 self.range[LEN]
             }
         }
@@ -181,5 +185,24 @@ macro_rules! define_histogram {
                 &self.bin as &[u64]
             }
         }
+
+        impl<'a> ::core::ops::AddAssign<&'a Self> for $name {
+            #[inline]
+            fn add_assign(&mut self, other: &Self) {
+                assert_eq!(self.range, other.range);
+                for (x, y) in self.bin.iter_mut().zip(other.bin.iter()) {
+                    *x += y;
+                }
+            }
+        }
+
+        impl ::core::ops::MulAssign<u64> for $name {
+            #[inline]
+            fn mul_assign(&mut self, other: u64) {
+                for x in self.bin.iter_mut() {
+                    *x *= other;
+                }
+            }
+        }
     );
 }

tests/histogram.rs

@@ -141,8 +141,43 @@ fn reset() {
 }
 
 #[test]
-fn minmax() {
+fn range_minmax() {
     let h = Histogram10::with_const_width(0., 100.);
-    assert_eq!(h.min(), 0.);
-    assert_eq!(h.max(), 100.);
+    assert_eq!(h.range_min(), 0.);
+    assert_eq!(h.range_max(), 100.);
+}
+
+#[test]
+fn add() {
+    let mut h1 = Histogram10::with_const_width(0., 100.);
+    let mut h2 = h1.clone();
+    let mut expected = h1.clone();
+
+    for i in 0..50 {
+        h1.add(f64::from(i)).unwrap();
+        expected.add(f64::from(i)).unwrap();
+    }
+    for i in 50..100 {
+        h2.add(f64::from(i)).unwrap();
+        expected.add(f64::from(i)).unwrap();
+    }
+    h1 += &h2;
+
+    assert_eq!(h1.bins(), expected.bins());
+}
+
+#[test]
+fn mul() {
+    let mut h = Histogram10::with_const_width(0., 100.);
+    let mut expected = h.clone();
+
+    for i in 0..100 {
+        h.add(f64::from(i)).unwrap();
+        expected.add(f64::from(i)).unwrap();
+        expected.add(f64::from(i)).unwrap();
+    }
+
+    h *= 2;
+
+    assert_eq!(h.bins(), expected.bins());
 }