From c64544baa870fde8ab9ab3d6add43978bfde09db Mon Sep 17 00:00:00 2001
From: Vinzent Steinberg <Vinzent.Steinberg@gmail.com>
Date: Tue, 6 Mar 2018 17:04:39 +0100
Subject: [PATCH] Implement iteration of histograms

---
 src/histogram.rs   | 38 ++++++++++++++++++++++++++++++++++++++
 tests/histogram.rs | 15 +++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/src/histogram.rs b/src/histogram.rs
index 17cef76..deaaf45 100644
--- a/src/histogram.rs
+++ b/src/histogram.rs
@@ -105,6 +105,44 @@ macro_rules! define_histogram {
             pub fn ranges(&self) -> &[f64] {
                 &self.range as &[f64]
             }
+
+            /// Return an iterator over the bins and corresponding ranges:
+            /// `((lower, upper), count)`
+            #[inline]
+            pub fn iter(&self) -> IterHistogram {
+                self.into_iter()
+            }
+        }
+
+        /// Iterate over all `(range, count)` pairs in the histogram.
+        pub struct IterHistogram<'a> {
+            remaining_bin: &'a [u64],
+            remaining_range: &'a [f64],
+        }
+
+        impl<'a> ::core::iter::Iterator for IterHistogram<'a> {
+            type Item = ((f64, f64), u64);
+            fn next(&mut self) -> Option<((f64, f64), u64)> {
+                if let Some((&bin, rest)) = self.remaining_bin.split_first() {
+                    let left = self.remaining_range[0];
+                    let right = self.remaining_range[1];
+                    self.remaining_bin = rest;
+                    self.remaining_range = &self.remaining_range[1..];
+                    return Some(((left, right), bin));
+                }
+                None
+            }
+        }
+
+        impl<'a> ::core::iter::IntoIterator for &'a $name {
+            type Item = ((f64, f64), u64);
+            type IntoIter = IterHistogram<'a>;
+            fn into_iter(self) -> IterHistogram<'a> {
+                IterHistogram {
+                    remaining_bin: self.bins(),
+                    remaining_range: self.ranges(),
+                }
+            }
         }
 
         impl $crate::Histogram for $name {
diff --git a/tests/histogram.rs b/tests/histogram.rs
index b6b8ddb..fc641ad 100644
--- a/tests/histogram.rs
+++ b/tests/histogram.rs
@@ -27,6 +27,21 @@ fn from_ranges() {
     assert_eq!(h.bins(), &[1, 0, 0, 0, 0, 0, 1, 0, 0, 2]);
 }
 
+#[test]
+fn iter() {
+    let mut h = Histogram10::from_ranges(
+        [0., 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8, 0.9, 1.0, 2.0].iter().cloned()).unwrap();
+    for &i in &[0.05, 0.7, 1.0, 1.5] {
+        h.add(i).unwrap();
+    }
+    let iterated: Vec<((f64, f64), u64)> = h.iter().collect();
+    assert_eq!(&iterated, &[
+        ((0., 0.1), 1), ((0.1, 0.2), 0), ((0.2, 0.3), 0), ((0.3, 0.4), 0),
+        ((0.4, 0.5), 0), ((0.5, 0.7), 0), ((0.7, 0.8), 1), ((0.8, 0.9), 0),
+        ((0.9, 1.0), 0), ((1.0, 2.0), 2)
+    ]);
+}
+
 #[test]
 fn from_ranges_infinity() {
     let inf = std::f64::INFINITY;