hashmap: Iterators for hashset diff, sym. diff, intersec, union
Implement the difference, union, etc iterators with the help of a custom iterator combinator with explicit closure environment. Reported issue #7814 to be able to use the std::iterator filter combinator.
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@ -16,9 +16,10 @@
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#[mutable_doc];
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use container::{Container, Mutable, Map, MutableMap, Set, MutableSet};
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use clone::Clone;
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use cmp::{Eq, Equiv};
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use hash::Hash;
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use iterator::{Iterator, IteratorUtil, FromIterator};
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use iterator::{Iterator, IteratorUtil, FromIterator, ChainIterator};
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use num;
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use option::{None, Option, Some};
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use rand::RngUtil;
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@ -703,25 +704,24 @@ impl<T:Hash + Eq> Set<T> for HashSet<T> {
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/// Visit the values representing the difference
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fn difference(&self, other: &HashSet<T>, f: &fn(&T) -> bool) -> bool {
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self.iter().advance(|v| other.contains(v) || f(v))
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self.difference_iter(other).advance(f)
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}
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/// Visit the values representing the symmetric difference
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fn symmetric_difference(&self,
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other: &HashSet<T>,
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f: &fn(&T) -> bool) -> bool {
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self.difference(other, |t| f(t)) && other.difference(self, |t| f(t))
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self.symmetric_difference_iter(other).advance(f)
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}
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/// Visit the values representing the intersection
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fn intersection(&self, other: &HashSet<T>, f: &fn(&T) -> bool) -> bool {
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self.iter().advance(|v| !other.contains(v) || f(v))
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self.intersection_iter(other).advance(f)
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}
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/// Visit the values representing the union
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fn union(&self, other: &HashSet<T>, f: &fn(&T) -> bool) -> bool {
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self.iter().advance(|t| f(t)) &&
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other.iter().advance(|v| self.contains(v) || f(v))
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self.union_iter(other).advance(f)
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}
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}
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@ -776,6 +776,33 @@ impl<T:Hash + Eq> HashSet<T> {
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pub fn iter<'a>(&'a self) -> HashSetIterator<'a, T> {
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HashSetIterator { iter: self.map.buckets.iter() }
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}
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/// Visit the values representing the difference
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pub fn difference_iter<'a>(&'a self, other: &'a HashSet<T>)
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-> SetAlgebraIter<'a, T> {
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EnvFilterIterator{iter: self.iter(), env: other,
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filter: |elt, other| !other.contains(elt) }
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}
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/// Visit the values representing the symmetric difference
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pub fn symmetric_difference_iter<'a>(&'a self, other: &'a HashSet<T>)
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-> ChainIterator<&'a T, SetAlgebraIter<'a, T>, SetAlgebraIter<'a, T>> {
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self.difference_iter(other).chain_(other.difference_iter(self))
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}
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/// Visit the values representing the intersection
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pub fn intersection_iter<'a>(&'a self, other: &'a HashSet<T>)
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-> SetAlgebraIter<'a, T> {
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EnvFilterIterator{iter: self.iter(), env: other,
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filter: |elt, other| other.contains(elt) }
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}
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/// Visit the values representing the union
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pub fn union_iter<'a>(&'a self, other: &'a HashSet<T>)
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-> ChainIterator<&'a T, HashSetIterator<'a, T>, SetAlgebraIter<'a, T>> {
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self.iter().chain_(other.difference_iter(self))
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}
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}
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impl<K: Eq + Hash, T: Iterator<K>> FromIterator<K, T> for HashSet<K> {
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@ -791,6 +818,39 @@ impl<K: Eq + Hash, T: Iterator<K>> FromIterator<K, T> for HashSet<K> {
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}
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}
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// FIXME #7814: use std::iterator::FilterIterator
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/// Building block for Set operation iterators
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pub struct EnvFilterIterator<A, Env, I> {
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priv env: Env,
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priv filter: &'static fn(&A, Env) -> bool,
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priv iter: I,
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}
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impl<'self, A, Env: Clone, I: Iterator<&'self A>> Iterator<&'self A>
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for EnvFilterIterator<A, Env, I> {
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#[inline]
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fn next(&mut self) -> Option<&'self A> {
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loop {
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match self.iter.next() {
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Some(elt) => if (self.filter)(elt, self.env.clone()) {
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return Some(elt)
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},
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None => return None,
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}
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}
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}
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#[inline]
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fn size_hint(&self) -> (uint, Option<uint>) {
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let (_, upper) = self.iter.size_hint();
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(0, upper)
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}
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}
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/// Set operations iterator
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pub type SetAlgebraIter<'self, T> =
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EnvFilterIterator<T, &'self HashSet<T>, HashSetIterator<'self, T>>;
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#[cfg(test)]
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mod test_map {
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@ -1126,7 +1186,7 @@ mod test_set {
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let mut i = 0;
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let expected = [3, 5, 11, 77];
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for a.intersection(&b) |x| {
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for a.intersection_iter(&b).advance |x| {
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assert!(expected.contains(x));
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i += 1
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}
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@ -1149,7 +1209,7 @@ mod test_set {
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let mut i = 0;
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let expected = [1, 5, 11];
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for a.difference(&b) |x| {
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for a.difference_iter(&b).advance |x| {
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assert!(expected.contains(x));
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i += 1
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}
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@ -1175,7 +1235,7 @@ mod test_set {
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let mut i = 0;
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let expected = [-2, 1, 5, 11, 14, 22];
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for a.symmetric_difference(&b) |x| {
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for a.symmetric_difference_iter(&b).advance |x| {
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assert!(expected.contains(x));
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i += 1
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}
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@ -1205,7 +1265,7 @@ mod test_set {
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let mut i = 0;
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let expected = [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24];
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for a.union(&b) |x| {
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for a.union_iter(&b).advance |x| {
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assert!(expected.contains(x));
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i += 1
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}
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