auto merge of #16582 : Gankro/rust/bitv, r=alexcrichton

This was bothering me (and some other people). The macro was necessary in a transient step of my development, but I converged on a design where it was unnecessary, but it didn't really click that that had happened.

This fixes it up.

src/libcollections/bitv.rs

@@ -66,7 +66,7 @@ use core::prelude::*;
 use core::cmp;
 use core::default::Default;
 use core::fmt;
-use core::iter::Take;
+use core::iter::{Chain, Enumerate, Repeat, Skip, Take};
 use core::iter;
 use core::slice;
 use core::uint;
@@ -75,25 +75,22 @@ use std::hash;
 use {Mutable, Set, MutableSet, MutableSeq};
 use vec::Vec;
 
+type MatchWords<'a> = Chain<MaskWords<'a>, Skip<Take<Enumerate<Repeat<uint>>>>>;
 // Take two BitV's, and return iterators of their words, where the shorter one
 // has been padded with 0's
-macro_rules! match_words(
-    ($a_expr:expr, $b_expr:expr) => ({
-        let a = $a_expr;
-        let b = $b_expr;
-        let a_len = a.storage.len();
-        let b_len = b.storage.len();
+fn match_words <'a,'b>(a: &'a Bitv, b: &'b Bitv) -> (MatchWords<'a>, MatchWords<'b>) {
+    let a_len = a.storage.len();
+    let b_len = b.storage.len();
 
-        // have to uselessly pretend to pad the longer one for type matching
-        if a_len < b_len {
-            (a.mask_words(0).chain(iter::Repeat::new(0u).enumerate().take(b_len).skip(a_len)),
-             b.mask_words(0).chain(iter::Repeat::new(0u).enumerate().take(0).skip(0)))
-        } else {
-            (a.mask_words(0).chain(iter::Repeat::new(0u).enumerate().take(0).skip(0)),
-             b.mask_words(0).chain(iter::Repeat::new(0u).enumerate().take(a_len).skip(b_len)))
-        }
-    })
-)
+    // have to uselessly pretend to pad the longer one for type matching
+    if a_len < b_len {
+        (a.mask_words(0).chain(Repeat::new(0u).enumerate().take(b_len).skip(a_len)),
+         b.mask_words(0).chain(Repeat::new(0u).enumerate().take(0).skip(0)))
+    } else {
+        (a.mask_words(0).chain(Repeat::new(0u).enumerate().take(0).skip(0)),
+         b.mask_words(0).chain(Repeat::new(0u).enumerate().take(a_len).skip(b_len)))
+    }
+}
 
 static TRUE: bool = true;
 static FALSE: bool = false;
@@ -1014,7 +1011,7 @@ impl Extendable<bool> for BitvSet {
 impl PartialOrd for BitvSet {
     #[inline]
     fn partial_cmp(&self, other: &BitvSet) -> Option<Ordering> {
-        let (a_iter, b_iter) = match_words!(self.get_ref(), other.get_ref());
+        let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
         iter::order::partial_cmp(a_iter, b_iter)
     }
 }
@@ -1022,7 +1019,7 @@ impl PartialOrd for BitvSet {
 impl Ord for BitvSet {
     #[inline]
     fn cmp(&self, other: &BitvSet) -> Ordering {
-        let (a_iter, b_iter) = match_words!(self.get_ref(), other.get_ref());
+        let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
         iter::order::cmp(a_iter, b_iter)
     }
 }
@@ -1030,7 +1027,7 @@ impl Ord for BitvSet {
 impl cmp::PartialEq for BitvSet {
     #[inline]
     fn eq(&self, other: &BitvSet) -> bool {
-        let (a_iter, b_iter) = match_words!(self.get_ref(), other.get_ref());
+        let (a_iter, b_iter) = match_words(self.get_ref(), other.get_ref());
         iter::order::eq(a_iter, b_iter)
     }
 }
@@ -1191,10 +1188,10 @@ impl BitvSet {
         self_bitv.reserve(other_bitv.capacity());
 
         // virtually pad other with 0's for equal lengths
-        let self_len = self_bitv.storage.len();
-        let other_len =  other_bitv.storage.len();
-        let mut other_words = other_bitv.mask_words(0)
-         .chain(iter::Repeat::new(0u).enumerate().take(self_len).skip(other_len));
+        let mut other_words = {
+            let (_, result) = match_words(self_bitv, other_bitv);
+            result
+        };
 
         // Apply values found in other
         for (i, w) in other_words {
@@ -1524,7 +1521,7 @@ impl Set<uint> for BitvSet {
 
     #[inline]
     fn is_disjoint(&self, other: &BitvSet) -> bool {
-        self.intersection(other).count() > 0
+        self.intersection(other).next().is_none()
     }
 
     #[inline]
@@ -2266,6 +2263,24 @@ mod tests {
         assert!(set1.is_subset(&set2)); // { 2 }  { 2, 4 }
     }
 
+    #[test]
+    fn test_bitv_set_is_disjoint() {
+        let a = BitvSet::from_bitv(from_bytes([0b10100010]));
+        let b = BitvSet::from_bitv(from_bytes([0b01000000]));
+        let c = BitvSet::new();
+        let d = BitvSet::from_bitv(from_bytes([0b00110000]));
+
+        assert!(!a.is_disjoint(&d));
+        assert!(!d.is_disjoint(&a));
+
+        assert!(a.is_disjoint(&b))
+        assert!(a.is_disjoint(&c))
+        assert!(b.is_disjoint(&a))
+        assert!(b.is_disjoint(&c))
+        assert!(c.is_disjoint(&a))
+        assert!(c.is_disjoint(&b))
+    }
+
     #[test]
     fn test_bitv_set_intersect_with() {
         // Explicitly 0'ed bits