bitv: Fix all() for nbits that are multiples of u32::BITS
The old logic would be ok with *either* 0 or all 1s in the last word, because it didn't compute a proper mask for the case where nbits is an exact multiple of u32::BITS. Add mask_for_bits() to compute this properly, and use it in all(). Add all/none assertions to most of the tests. Note in particular, the all-zero bitv in test_32_elements() was incorrectly all()==true before this patch.
This commit is contained in:
Josh Stone
Alexis Beingessner
parent
8f194de95d
commit
3deb97f5d0
1 changed files with 43 additions and 8 deletions
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@ -174,6 +174,12 @@ fn blocks_for_bits(bits: uint) -> uint {
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}
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/// Computes the bitmask for the final word of the vector
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fn mask_for_bits(bits: uint) -> u32 {
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// Note especially that a perfect multiple of u32::BITS should mask all 1s.
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!0u32 >> (u32::BITS - bits % u32::BITS) % u32::BITS
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}
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impl Bitv {
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/// Applies the given operation to the blocks of self and other, and sets self to
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/// be the result.
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@ -526,7 +532,7 @@ impl Bitv {
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last_word = elem;
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tmp == !0u32
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// and then check the last one has enough ones
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}) && (last_word == ((1 << self.nbits % u32::BITS) - 1) || last_word == !0u32)
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}) && (last_word == mask_for_bits(self.nbits))
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}
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/// Returns an iterator over the elements of the vector in order.
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@ -788,15 +794,15 @@ impl Bitv {
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let new_nblocks = blocks_for_bits(new_nbits);
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let full_value = if value { !0 } else { 0 };
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// Correct the old tail word
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// Correct the old tail word, setting or clearing formerly unused bits
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let old_last_word = blocks_for_bits(self.nbits) - 1;
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if self.nbits % u32::BITS > 0 {
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let overhang = self.nbits % u32::BITS; // # of already-used bits
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let mask = !((1 << overhang) - 1); // e.g. 5 unused bits => 111110..0
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let mask = mask_for_bits(self.nbits);
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if value {
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self.storage[old_last_word] |= mask;
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self.storage[old_last_word] |= !mask;
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} else {
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self.storage[old_last_word] &= !mask;
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// Extra bits are already supposed to be zero by invariant, but play it safe...
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self.storage[old_last_word] &= mask;
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}
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}
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@ -1808,14 +1814,17 @@ mod tests {
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let act = Bitv::new();
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let exp = Vec::from_elem(0u, false);
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assert!(act.eq_vec(exp.as_slice()));
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assert!(act.none() && act.all());
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}
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#[test]
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fn test_1_element() {
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let mut act = Bitv::from_elem(1u, false);
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assert!(act.eq_vec(&[false]));
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assert!(act.none() && !act.all());
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act = Bitv::from_elem(1u, true);
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assert!(act.eq_vec(&[true]));
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assert!(!act.none() && act.all());
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}
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#[test]
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@ -1824,6 +1833,7 @@ mod tests {
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b.set(0, true);
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b.set(1, false);
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assert_eq!(b.to_string(), "10");
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assert!(!b.none() && !b.all());
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}
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#[test]
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@ -1834,10 +1844,12 @@ mod tests {
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act = Bitv::from_elem(10u, false);
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assert!((act.eq_vec(
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&[false, false, false, false, false, false, false, false, false, false])));
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assert!(act.none() && !act.all());
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// all 1
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act = Bitv::from_elem(10u, true);
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assert!((act.eq_vec(&[true, true, true, true, true, true, true, true, true, true])));
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assert!(!act.none() && act.all());
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// mixed
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act = Bitv::from_elem(10u, false);
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@ -1847,6 +1859,7 @@ mod tests {
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act.set(3u, true);
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act.set(4u, true);
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assert!((act.eq_vec(&[true, true, true, true, true, false, false, false, false, false])));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(10u, false);
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@ -1856,6 +1869,7 @@ mod tests {
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act.set(8u, true);
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act.set(9u, true);
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assert!((act.eq_vec(&[false, false, false, false, false, true, true, true, true, true])));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(10u, false);
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@ -1864,6 +1878,7 @@ mod tests {
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act.set(6u, true);
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act.set(9u, true);
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assert!((act.eq_vec(&[true, false, false, true, false, false, true, false, false, true])));
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assert!(!act.none() && !act.all());
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}
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#[test]
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@ -1876,6 +1891,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false]));
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assert!(act.none() && !act.all());
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// all 1
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act = Bitv::from_elem(31u, true);
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@ -1883,6 +1899,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true]));
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assert!(!act.none() && act.all());
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// mixed
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act = Bitv::from_elem(31u, false);
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@ -1898,6 +1915,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(31u, false);
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@ -1913,6 +1931,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, true, true, true, true, true, true, true,
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false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(31u, false);
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@ -1927,6 +1946,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, true, true, true, true, true, true, true]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(31u, false);
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@ -1937,6 +1957,7 @@ mod tests {
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&[false, false, false, true, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, false, false, false, false, false, false,
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false, false, false, false, false, false, true]));
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assert!(!act.none() && !act.all());
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}
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#[test]
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@ -1949,6 +1970,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false]));
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assert!(act.none() && !act.all());
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// all 1
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act = Bitv::from_elem(32u, true);
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@ -1956,6 +1978,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true, true]));
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assert!(!act.none() && act.all());
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// mixed
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act = Bitv::from_elem(32u, false);
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@ -1971,6 +1994,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(32u, false);
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@ -1986,6 +2010,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, true, true, true, true, true, true, true,
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false, false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(32u, false);
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@ -2001,6 +2026,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, true, true, true, true, true, true, true, true]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(32u, false);
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@ -2012,6 +2038,7 @@ mod tests {
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&[false, false, false, true, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, false, false, false, false, false, false,
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false, false, false, false, false, false, true, true]));
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assert!(!act.none() && !act.all());
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}
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#[test]
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@ -2024,6 +2051,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false]));
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assert!(act.none() && !act.all());
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// all 1
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act = Bitv::from_elem(33u, true);
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@ -2031,6 +2059,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true]));
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assert!(!act.none() && act.all());
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// mixed
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act = Bitv::from_elem(33u, false);
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@ -2046,6 +2075,7 @@ mod tests {
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&[true, true, true, true, true, true, true, true, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(33u, false);
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@ -2061,6 +2091,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, true, true, true, true, true, true, true,
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false, false, false, false, false, false, false, false, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(33u, false);
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@ -2076,6 +2107,7 @@ mod tests {
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&[false, false, false, false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false, false, false, false,
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false, false, true, true, true, true, true, true, true, true, false]));
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assert!(!act.none() && !act.all());
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// mixed
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act = Bitv::from_elem(33u, false);
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@ -2088,6 +2120,7 @@ mod tests {
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&[false, false, false, true, false, false, false, false, false, false, false, false,
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false, false, false, false, false, true, false, false, false, false, false, false,
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false, false, false, false, false, false, true, true, true]));
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assert!(!act.none() && !act.all());
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}
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#[test]
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@ -2234,15 +2267,17 @@ mod tests {
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#[test]
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fn test_small_clear() {
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let mut b = Bitv::from_elem(14, true);
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assert!(!b.none() && b.all());
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b.clear();
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assert!(b.none());
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assert!(b.none() && !b.all());
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}
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#[test]
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fn test_big_clear() {
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let mut b = Bitv::from_elem(140, true);
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assert!(!b.none() && b.all());
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b.clear();
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assert!(b.none());
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assert!(b.none() && !b.all());
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}
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#[test]
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