Rename Iterator::len to count

This commit carries out the request from issue #14678:

> The method `Iterator::len()` is surprising, as all the other uses of
> `len()` do not consume the value. `len()` would make more sense to be
> called `count()`, but that would collide with the current
> `Iterator::count(|T| -> bool) -> unit` method. That method, however, is
> a bit redundant, and can be easily replaced with
> `iter.filter(|x| x < 5).count()`.
> After this change, we could then define the `len()` method
> on `iter::ExactSize`.

Closes #14678.

[breaking-change]

6 files changed, 34 insertions, 34 deletions

diff --git a/src/libcollections/bitv.rs b/src/libcollections/bitv.rs
index 11c777034fe..58f081b25e3 100644
--- a/src/libcollections/bitv.rs
+++ b/src/libcollections/bitv.rs
@@ -241,17 +241,17 @@ enum Op {Union, Intersect, Assign, Difference}
 /// bv.set(5, true);
 /// bv.set(7, true);
 /// println!("{}", bv.to_str());
-/// println!("total bits set to true: {}", bv.iter().count(|x| x));
+/// println!("total bits set to true: {}", bv.iter().filter(|x| *x).count());
 ///
 /// // flip all values in bitvector, producing non-primes less than 10
 /// bv.negate();
 /// println!("{}", bv.to_str());
-/// println!("total bits set to true: {}", bv.iter().count(|x| x));
+/// println!("total bits set to true: {}", bv.iter().filter(|x| *x).count());
 ///
 /// // reset bitvector to empty
 /// bv.clear();
 /// println!("{}", bv.to_str());
-/// println!("total bits set to true: {}", bv.iter().count(|x| x));
+/// println!("total bits set to true: {}", bv.iter().filter(|x| *x).count());
 /// ```
 #[deriving(Clone)]
 pub struct Bitv {
@@ -461,7 +461,7 @@ impl Bitv {
     /// bv.set(5, true);
     /// bv.set(8, true);
     /// // Count bits set to 1; result should be 5
-    /// println!("{}", bv.iter().count(|x| x));
+    /// println!("{}", bv.iter().filter(|x| *x).count());
     /// ```
     #[inline]
     pub fn iter<'a>(&'a self) -> Bits<'a> {
diff --git a/src/libcollections/dlist.rs b/src/libcollections/dlist.rs
index 8e3a49eecf3..94c617b58e8 100644
--- a/src/libcollections/dlist.rs
+++ b/src/libcollections/dlist.rs
@@ -1131,7 +1131,7 @@ mod tests {
         let v = &[0, ..128];
         let m: DList<int> = v.iter().map(|&x|x).collect();
         b.iter(|| {
-            assert!(m.iter().len() == 128);
+            assert!(m.iter().count() == 128);
         })
     }
     #[bench]
@@ -1139,7 +1139,7 @@ mod tests {
         let v = &[0, ..128];
         let mut m: DList<int> = v.iter().map(|&x|x).collect();
         b.iter(|| {
-            assert!(m.mut_iter().len() == 128);
+            assert!(m.mut_iter().count() == 128);
         })
     }
     #[bench]
@@ -1147,7 +1147,7 @@ mod tests {
         let v = &[0, ..128];
         let m: DList<int> = v.iter().map(|&x|x).collect();
         b.iter(|| {
-            assert!(m.iter().rev().len() == 128);
+            assert!(m.iter().rev().count() == 128);
         })
     }
     #[bench]
@@ -1155,7 +1155,7 @@ mod tests {
         let v = &[0, ..128];
         let mut m: DList<int> = v.iter().map(|&x|x).collect();
         b.iter(|| {
-            assert!(m.mut_iter().rev().len() == 128);
+            assert!(m.mut_iter().rev().count() == 128);
         })
     }
 }
diff --git a/src/libcollections/slice.rs b/src/libcollections/slice.rs
index 0b339a97262..e631b8b77cf 100644
--- a/src/libcollections/slice.rs
+++ b/src/libcollections/slice.rs
@@ -2155,7 +2155,7 @@ mod tests {
     #[test]
     fn test_mut_splitator() {
         let mut xs = [0,1,0,2,3,0,0,4,5,0];
-        assert_eq!(xs.mut_split(|x| *x == 0).len(), 6);
+        assert_eq!(xs.mut_split(|x| *x == 0).count(), 6);
         for slice in xs.mut_split(|x| *x == 0) {
             slice.reverse();
         }
diff --git a/src/libcollections/smallintmap.rs b/src/libcollections/smallintmap.rs
index 829986e64ee..f3118181bdc 100644
--- a/src/libcollections/smallintmap.rs
+++ b/src/libcollections/smallintmap.rs
@@ -31,7 +31,7 @@ pub struct SmallIntMap<T> {
 impl<V> Container for SmallIntMap<V> {
     /// Return the number of elements in the map
     fn len(&self) -> uint {
-        self.v.iter().count(|elt| elt.is_some())
+        self.v.iter().filter(|elt| elt.is_some()).count()
     }
 
     /// Return true if there are no elements in the map
diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index ab1b1d1bd81..5fd133b450f 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -2181,7 +2181,7 @@ mod bench {
         let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
         let len = s.char_len();
 
-        b.iter(|| assert_eq!(s.chars().len(), len));
+        b.iter(|| assert_eq!(s.chars().count(), len));
     }
 
     #[bench]
@@ -2194,7 +2194,7 @@ mod bench {
         Mary had a little lamb, Little lamb";
         let len = s.char_len();
 
-        b.iter(|| assert_eq!(s.chars().len(), len));
+        b.iter(|| assert_eq!(s.chars().count(), len));
     }
 
     #[bench]
@@ -2202,7 +2202,7 @@ mod bench {
         let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
         let len = s.char_len();
 
-        b.iter(|| assert_eq!(s.chars().rev().len(), len));
+        b.iter(|| assert_eq!(s.chars().rev().count(), len));
     }
 
     #[bench]
@@ -2210,7 +2210,7 @@ mod bench {
         let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
         let len = s.char_len();
 
-        b.iter(|| assert_eq!(s.char_indices().len(), len));
+        b.iter(|| assert_eq!(s.char_indices().count(), len));
     }
 
     #[bench]
@@ -2218,14 +2218,14 @@ mod bench {
         let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
         let len = s.char_len();
 
-        b.iter(|| assert_eq!(s.char_indices().rev().len(), len));
+        b.iter(|| assert_eq!(s.char_indices().rev().count(), len));
     }
 
     #[bench]
     fn split_unicode_ascii(b: &mut Bencher) {
         let s = "ประเทศไทย中华Việt Namประเทศไทย中华Việt Nam";
 
-        b.iter(|| assert_eq!(s.split('V').len(), 3));
+        b.iter(|| assert_eq!(s.split('V').count(), 3));
     }
 
     #[bench]
@@ -2240,16 +2240,16 @@ mod bench {
         }
         let s = "ประเทศไทย中华Việt Namประเทศไทย中华Việt Nam";
 
-        b.iter(|| assert_eq!(s.split(NotAscii('V')).len(), 3));
+        b.iter(|| assert_eq!(s.split(NotAscii('V')).count(), 3));
     }
 
 
     #[bench]
     fn split_ascii(b: &mut Bencher) {
         let s = "Mary had a little lamb, Little lamb, little-lamb.";
-        let len = s.split(' ').len();
+        let len = s.split(' ').count();
 
-        b.iter(|| assert_eq!(s.split(' ').len(), len));
+        b.iter(|| assert_eq!(s.split(' ').count(), len));
     }
 
     #[bench]
@@ -2264,34 +2264,34 @@ mod bench {
             fn only_ascii(&self) -> bool { false }
         }
         let s = "Mary had a little lamb, Little lamb, little-lamb.";
-        let len = s.split(' ').len();
+        let len = s.split(' ').count();
 
-        b.iter(|| assert_eq!(s.split(NotAscii(' ')).len(), len));
+        b.iter(|| assert_eq!(s.split(NotAscii(' ')).count(), len));
     }
 
     #[bench]
     fn split_extern_fn(b: &mut Bencher) {
         let s = "Mary had a little lamb, Little lamb, little-lamb.";
-        let len = s.split(' ').len();
+        let len = s.split(' ').count();
         fn pred(c: char) -> bool { c == ' ' }
 
-        b.iter(|| assert_eq!(s.split(pred).len(), len));
+        b.iter(|| assert_eq!(s.split(pred).count(), len));
     }
 
     #[bench]
     fn split_closure(b: &mut Bencher) {
         let s = "Mary had a little lamb, Little lamb, little-lamb.";
-        let len = s.split(' ').len();
+        let len = s.split(' ').count();
 
-        b.iter(|| assert_eq!(s.split(|c: char| c == ' ').len(), len));
+        b.iter(|| assert_eq!(s.split(|c: char| c == ' ').count(), len));
     }
 
     #[bench]
     fn split_slice(b: &mut Bencher) {
         let s = "Mary had a little lamb, Little lamb, little-lamb.";
-        let len = s.split(' ').len();
+        let len = s.split(' ').count();
 
-        b.iter(|| assert_eq!(s.split(&[' ']).len(), len));
+        b.iter(|| assert_eq!(s.split(&[' ']).count(), len));
     }
 
     #[bench]
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index aa80a131811..6ca21262f51 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -1772,23 +1772,23 @@ mod tests {
         assert_eq!(v.pop(), Some(()));
         assert_eq!(v.pop(), None);
 
-        assert_eq!(v.iter().len(), 0);
+        assert_eq!(v.iter().count(), 0);
         v.push(());
-        assert_eq!(v.iter().len(), 1);
+        assert_eq!(v.iter().count(), 1);
         v.push(());
-        assert_eq!(v.iter().len(), 2);
+        assert_eq!(v.iter().count(), 2);
 
         for &() in v.iter() {}
 
-        assert_eq!(v.mut_iter().len(), 2);
+        assert_eq!(v.mut_iter().count(), 2);
         v.push(());
-        assert_eq!(v.mut_iter().len(), 3);
+        assert_eq!(v.mut_iter().count(), 3);
         v.push(());
-        assert_eq!(v.mut_iter().len(), 4);
+        assert_eq!(v.mut_iter().count(), 4);
 
         for &() in v.mut_iter() {}
         unsafe { v.set_len(0); }
-        assert_eq!(v.mut_iter().len(), 0);
+        assert_eq!(v.mut_iter().count(), 0);
     }
 
     #[test]