Rollup merge of rust-lang#22887 - JP-Ellis:master, r=huonw

 Updated the function to allow comparisons between different types since PartialOrd and PartialEq allow this.

Author: Manishearth

src/libcore/iter.rs

@@ -2874,10 +2874,10 @@ pub mod order {
     use super::Iterator;
 
     /// Compare `a` and `b` for equality using `Eq`
-    pub fn equals<A, T, S>(mut a: T, mut b: S) -> bool where
+    pub fn equals<A, L, R>(mut a: L, mut b: R) -> bool where
         A: Eq,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+        L: Iterator<Item=A>,
+        R: Iterator<Item=A>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2889,10 +2889,10 @@ pub mod order {
     }
 
     /// Order `a` and `b` lexicographically using `Ord`
-    pub fn cmp<A, T, S>(mut a: T, mut b: S) -> cmp::Ordering where
+    pub fn cmp<A, L, R>(mut a: L, mut b: R) -> cmp::Ordering where
         A: Ord,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+        L: Iterator<Item=A>,
+        R: Iterator<Item=A>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2908,10 +2908,8 @@ pub mod order {
     }
 
     /// Order `a` and `b` lexicographically using `PartialOrd`
-    pub fn partial_cmp<A, T, S>(mut a: T, mut b: S) -> Option<cmp::Ordering> where
-        A: PartialOrd,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+    pub fn partial_cmp<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> Option<cmp::Ordering> where
+        L::Item: PartialOrd<R::Item>
     {
         loop {
             match (a.next(), b.next()) {
@@ -2927,10 +2925,8 @@ pub mod order {
     }
 
     /// Compare `a` and `b` for equality (Using partial equality, `PartialEq`)
-    pub fn eq<A, B, L, R>(mut a: L, mut b: R) -> bool where
-        A: PartialEq<B>,
-        L: Iterator<Item=A>,
-        R: Iterator<Item=B>,
+    pub fn eq<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialEq<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2942,10 +2938,8 @@ pub mod order {
     }
 
     /// Compare `a` and `b` for nonequality (Using partial equality, `PartialEq`)
-    pub fn ne<A, B, L, R>(mut a: L, mut b: R) -> bool where
-        A: PartialEq<B>,
-        L: Iterator<Item=A>,
-        R: Iterator<Item=B>,
+    pub fn ne<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialEq<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2957,10 +2951,8 @@ pub mod order {
     }
 
     /// Return `a` < `b` lexicographically (Using partial order, `PartialOrd`)
-    pub fn lt<A, T, S>(mut a: T, mut b: S) -> bool where
-        A: PartialOrd,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+    pub fn lt<R: Iterator, L: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialOrd<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2973,10 +2965,8 @@ pub mod order {
     }
 
     /// Return `a` <= `b` lexicographically (Using partial order, `PartialOrd`)
-    pub fn le<A, T, S>(mut a: T, mut b: S) -> bool where
-        A: PartialOrd,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+    pub fn le<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialOrd<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -2989,10 +2979,8 @@ pub mod order {
     }
 
     /// Return `a` > `b` lexicographically (Using partial order, `PartialOrd`)
-    pub fn gt<A, T, S>(mut a: T, mut b: S) -> bool where
-        A: PartialOrd,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+    pub fn gt<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialOrd<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {
@@ -3005,10 +2993,8 @@ pub mod order {
     }
 
     /// Return `a` >= `b` lexicographically (Using partial order, `PartialOrd`)
-    pub fn ge<A, T, S>(mut a: T, mut b: S) -> bool where
-        A: PartialOrd,
-        T: Iterator<Item=A>,
-        S: Iterator<Item=A>,
+    pub fn ge<L: Iterator, R: Iterator>(mut a: L, mut b: R) -> bool where
+        L::Item: PartialOrd<R::Item>,
     {
         loop {
             match (a.next(), b.next()) {