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Fix the difference method on bit vectors #4546

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Merged
merged 1 commit into from
Jan 20, 2013
Merged

Fix the difference method on bit vectors #4546

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37 changes: 32 additions & 5 deletions src/libstd/bitv.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,7 @@ impl SmallBitv {

#[inline(always)]
fn difference(s: &SmallBitv, nbits: uint) -> bool {
self.bits_op(s.bits, nbits, |u1, u2| u1 ^ u2)
self.bits_op(s.bits, nbits, |u1, u2| u1 & !u2)
}

#[inline(always)]
Expand Down Expand Up @@ -180,10 +180,7 @@ impl BigBitv {

#[inline(always)]
fn difference(b: &BigBitv, nbits: uint) -> bool {
self.invert();
let b = self.intersect(b, nbits);
self.invert();
b
self.process(b, nbits, difference)
}

#[inline(always)]
Expand Down Expand Up @@ -567,6 +564,8 @@ pure fn lor(w0: uint, w1: uint) -> uint { return w0 | w1; }

pure fn land(w0: uint, w1: uint) -> uint { return w0 & w1; }

pure fn difference(w0: uint, w1: uint) -> uint { return w0 & !w1; }

pure fn right(_w0: uint, w1: uint) -> uint { return w1; }

impl Bitv: ops::Index<uint,bool> {
Expand Down Expand Up @@ -954,6 +953,34 @@ mod tests {
let bools = ~[false, false, true, false, false, true, true, false];
assert from_bytes([0b00100110]).to_bools() == bools;
}

#[test]
fn test_small_difference() {
let b1 = Bitv(3, false);
let b2 = Bitv(3, false);
b1.set(0, true);
b1.set(1, true);
b2.set(1, true);
b2.set(2, true);
assert b1.difference(&b2);
assert b1[0];
assert !b1[1];
assert !b1[2];
}

#[test]
fn test_big_difference() {
let b1 = Bitv(100, false);
let b2 = Bitv(100, false);
b1.set(0, true);
b1.set(40, true);
b2.set(40, true);
b2.set(80, true);
assert b1.difference(&b2);
assert b1[0];
assert !b1[40];
assert !b1[80];
}
}

//
Expand Down