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auto merge of #8428 : blake2-ppc/rust/peekable-iterators, r=thestinger

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Peekable changes by @SimonSapin and original PR is #8396
This commit is contained in:
bors 2013-08-12 04:29:11 -07:00
commit ecfc9a8223
2 changed files with 138 additions and 107 deletions
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134
src/libextra/treemap.rs
View file

@ -14,7 +14,8 @@
use std::util::{swap, replace}; use std::util::{swap, replace};
use std::iterator::{FromIterator, Extendable}; use std::iterator::{FromIterator, Extendable, Peekable};
use std::cmp::Ordering;
// This is implemented as an AA tree, which is a simplified variation of // This is implemented as an AA tree, which is a simplified variation of
// a red-black tree where red (horizontal) nodes can only be added // a red-black tree where red (horizontal) nodes can only be added
@ -529,24 +530,24 @@ impl<T: TotalOrd> TreeSet<T> {
/// Visit the values (in-order) representing the difference /// Visit the values (in-order) representing the difference
pub fn difference<'a>(&'a self, other: &'a TreeSet<T>) -> Difference<'a, T> { pub fn difference<'a>(&'a self, other: &'a TreeSet<T>) -> Difference<'a, T> {
Difference{a: Focus::new(self.iter()), b: Focus::new(other.iter())} Difference{a: self.iter().peekable(), b: other.iter().peekable()}
} }
/// Visit the values (in-order) representing the symmetric difference /// Visit the values (in-order) representing the symmetric difference
pub fn symmetric_difference<'a>(&'a self, other: &'a TreeSet<T>) pub fn symmetric_difference<'a>(&'a self, other: &'a TreeSet<T>)
-> SymDifference<'a, T> { -> SymDifference<'a, T> {
SymDifference{a: Focus::new(self.iter()), b: Focus::new(other.iter())} SymDifference{a: self.iter().peekable(), b: other.iter().peekable()}
} }
/// Visit the values (in-order) representing the intersection /// Visit the values (in-order) representing the intersection
pub fn intersection<'a>(&'a self, other: &'a TreeSet<T>) pub fn intersection<'a>(&'a self, other: &'a TreeSet<T>)
-> Intersection<'a, T> { -> Intersection<'a, T> {
Intersection{a: Focus::new(self.iter()), b: Focus::new(other.iter())} Intersection{a: self.iter().peekable(), b: other.iter().peekable()}
} }
/// Visit the values (in-order) representing the union /// Visit the values (in-order) representing the union
pub fn union<'a>(&'a self, other: &'a TreeSet<T>) -> Union<'a, T> { pub fn union<'a>(&'a self, other: &'a TreeSet<T>) -> Union<'a, T> {
Union{a: Focus::new(self.iter()), b: Focus::new(other.iter())} Union{a: self.iter().peekable(), b: other.iter().peekable()}
} }
} }
@ -560,61 +561,47 @@ pub struct TreeSetRevIterator<'self, T> {
priv iter: TreeMapRevIterator<'self, T, ()> priv iter: TreeMapRevIterator<'self, T, ()>
} }
// Encapsulate an iterator and hold its latest value until stepped forward
struct Focus<A, T> {
priv iter: T,
priv focus: Option<A>,
}
impl<A, T: Iterator<A>> Focus<A, T> {
fn new(mut it: T) -> Focus<A, T> {
Focus{focus: it.next(), iter: it}
}
fn step(&mut self) {
self.focus = self.iter.next()
}
}
/// Lazy iterator producing elements in the set difference (in-order) /// Lazy iterator producing elements in the set difference (in-order)
pub struct Difference<'self, T> { pub struct Difference<'self, T> {
priv a: Focus<&'self T, TreeSetIterator<'self, T>>, priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
priv b: Focus<&'self T, TreeSetIterator<'self, T>>, priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
} }
/// Lazy iterator producing elements in the set symmetric difference (in-order) /// Lazy iterator producing elements in the set symmetric difference (in-order)
pub struct SymDifference<'self, T> { pub struct SymDifference<'self, T> {
priv a: Focus<&'self T, TreeSetIterator<'self, T>>, priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
priv b: Focus<&'self T, TreeSetIterator<'self, T>>, priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
} }
/// Lazy iterator producing elements in the set intersection (in-order) /// Lazy iterator producing elements in the set intersection (in-order)
pub struct Intersection<'self, T> { pub struct Intersection<'self, T> {
priv a: Focus<&'self T, TreeSetIterator<'self, T>>, priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
priv b: Focus<&'self T, TreeSetIterator<'self, T>>, priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
} }
/// Lazy iterator producing elements in the set intersection (in-order) /// Lazy iterator producing elements in the set intersection (in-order)
pub struct Union<'self, T> { pub struct Union<'self, T> {
priv a: Focus<&'self T, TreeSetIterator<'self, T>>, priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
priv b: Focus<&'self T, TreeSetIterator<'self, T>>, priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
}
/// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
fn cmp_opt<T: TotalOrd>(x: Option<&T>, y: Option<&T>,
short: Ordering, long: Ordering) -> Ordering {
match (x, y) {
(None , _ ) => short,
(_ , None ) => long,
(Some(x1), Some(y1)) => x1.cmp(y1),
}
} }
impl<'self, T: TotalOrd> Iterator<&'self T> for Difference<'self, T> { impl<'self, T: TotalOrd> Iterator<&'self T> for Difference<'self, T> {
fn next(&mut self) -> Option<&'self T> { fn next(&mut self) -> Option<&'self T> {
loop { loop {
match (self.a.focus, self.b.focus) { match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
(None , _ ) => return None, Less => return self.a.next(),
(ret , None ) => { self.a.step(); return ret }, Equal => { self.a.next(); self.b.next(); }
(Some(a1), Some(b1)) => { Greater => { self.b.next(); }
let cmp = a1.cmp(b1);
if cmp == Less {
self.a.step();
return Some(a1);
} else {
if cmp == Equal { self.a.step() }
self.b.step();
}
}
} }
} }
} }
@ -623,23 +610,10 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for Difference<'self, T> {
impl<'self, T: TotalOrd> Iterator<&'self T> for SymDifference<'self, T> { impl<'self, T: TotalOrd> Iterator<&'self T> for SymDifference<'self, T> {
fn next(&mut self) -> Option<&'self T> { fn next(&mut self) -> Option<&'self T> {
loop { loop {
match (self.a.focus, self.b.focus) { match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
(ret , None ) => { self.a.step(); return ret }, Less => return self.a.next(),
(None , ret ) => { self.b.step(); return ret }, Equal => { self.a.next(); self.b.next(); }
(Some(a1), Some(b1)) => { Greater => return self.b.next(),
let cmp = a1.cmp(b1);
if cmp == Less {
self.a.step();
return Some(a1);
} else {
self.b.step();
if cmp == Greater {
return Some(b1);
} else {
self.a.step();
}
}
}
} }
} }
} }
@ -648,20 +622,16 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for SymDifference<'self, T> {
impl<'self, T: TotalOrd> Iterator<&'self T> for Intersection<'self, T> { impl<'self, T: TotalOrd> Iterator<&'self T> for Intersection<'self, T> {
fn next(&mut self) -> Option<&'self T> { fn next(&mut self) -> Option<&'self T> {
loop { loop {
match (self.a.focus, self.b.focus) { let o_cmp = match (self.a.peek(), self.b.peek()) {
(None , _ ) => return None, (None , _ ) => None,
(_ , None ) => return None, (_ , None ) => None,
(Some(a1), Some(b1)) => { (Some(a1), Some(b1)) => Some(a1.cmp(b1)),
let cmp = a1.cmp(b1); };
if cmp == Less { match o_cmp {
self.a.step(); None => return None,
} else { Some(Less) => { self.a.next(); }
self.b.step(); Some(Equal) => { self.b.next(); return self.a.next() }
if cmp == Equal { Some(Greater) => { self.b.next(); }
return Some(a1);
}
}
},
} }
} }
} }
@ -670,22 +640,10 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for Intersection<'self, T> {
impl<'self, T: TotalOrd> Iterator<&'self T> for Union<'self, T> { impl<'self, T: TotalOrd> Iterator<&'self T> for Union<'self, T> {
fn next(&mut self) -> Option<&'self T> { fn next(&mut self) -> Option<&'self T> {
loop { loop {
match (self.a.focus, self.b.focus) { match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
(ret , None) => { self.a.step(); return ret }, Less => return self.a.next(),
(None , ret ) => { self.b.step(); return ret }, Equal => { self.b.next(); return self.a.next() }
(Some(a1), Some(b1)) => { Greater => return self.b.next(),
let cmp = a1.cmp(b1);
if cmp == Greater {
self.b.step();
return Some(b1);
} else {
self.a.step();
if cmp == Equal {
self.b.step();
}
return Some(a1);
}
}
} }
} }
} }

111
src/libstd/iterator.rs
View file

@ -156,6 +156,28 @@ pub trait Iterator<A> {
Enumerate{iter: self, count: 0} Enumerate{iter: self, count: 0}
} }
/// Creates an iterator that has a `.peek()` method
/// that returns a optional reference to the next element.
///
/// # Example
///
/// ~~~ {.rust}
/// let a = [100, 200, 300];
/// let mut it = xs.iter().map(|&x|x).peekable();
/// assert_eq!(it.peek().unwrap(), &100);
/// assert_eq!(it.next().unwrap(), 100);
/// assert_eq!(it.next().unwrap(), 200);
/// assert_eq!(it.peek().unwrap(), &300);
/// assert_eq!(it.peek().unwrap(), &300);
/// assert_eq!(it.next().unwrap(), 300);
/// assert!(it.peek().is_none());
/// assert!(it.next().is_none());
/// ~~~
fn peekable(self) -> Peekable<A, Self> {
Peekable{iter: self, peeked: None}
}
/// Creates an iterator which invokes the predicate on elements until it /// Creates an iterator which invokes the predicate on elements until it
/// returns false. Once the predicate returns false, all further elements are /// returns false. Once the predicate returns false, all further elements are
/// yielded. /// yielded.
@ -286,15 +308,15 @@ pub trait Iterator<A> {
///let xs = [1u, 4, 2, 3, 8, 9, 6]; ///let xs = [1u, 4, 2, 3, 8, 9, 6];
///let sum = xs.iter() ///let sum = xs.iter()
/// .map(|&x| x) /// .map(|&x| x)
/// .peek(|&x| debug!("filtering %u", x)) /// .inspect(|&x| debug!("filtering %u", x))
/// .filter(|&x| x % 2 == 0) /// .filter(|&x| x % 2 == 0)
/// .peek(|&x| debug!("%u made it through", x)) /// .inspect(|&x| debug!("%u made it through", x))
/// .sum(); /// .sum();
///println(sum.to_str()); ///println(sum.to_str());
/// ~~~ /// ~~~
#[inline] #[inline]
fn peek<'r>(self, f: &'r fn(&A)) -> Peek<'r, A, Self> { fn inspect<'r>(self, f: &'r fn(&A)) -> Inspect<'r, A, Self> {
Peek{iter: self, f: f} Inspect{iter: self, f: f}
} }
/// An adaptation of an external iterator to the for-loop protocol of rust. /// An adaptation of an external iterator to the for-loop protocol of rust.
@ -1059,6 +1081,38 @@ impl<A, T: RandomAccessIterator<A>> RandomAccessIterator<(uint, A)> for Enumerat
} }
} }
/// An iterator with a `peek()` that returns an optional reference to the next element.
pub struct Peekable<A, T> {
priv iter: T,
priv peeked: Option<A>,
}
impl<A, T: Iterator<A>> Iterator<A> for Peekable<A, T> {
#[inline]
fn next(&mut self) -> Option<A> {
if self.peeked.is_some() { self.peeked.take() }
else { self.iter.next() }
}
}
impl<'self, A, T: Iterator<A>> Peekable<A, T> {
/// Return a reference to the next element of the iterator with out advancing it,
/// or None if the iterator is exhausted.
#[inline]
pub fn peek(&'self mut self) -> Option<&'self A> {
match self.peeked {
Some(ref value) => Some(value),
None => {
self.peeked = self.iter.next();
match self.peeked {
Some(ref value) => Some(value),
None => None,
}
},
}
}
}
/// An iterator which rejects elements while `predicate` is true /// An iterator which rejects elements while `predicate` is true
pub struct SkipWhile<'self, A, T> { pub struct SkipWhile<'self, A, T> {
priv iter: T, priv iter: T,
@ -1329,14 +1383,14 @@ impl<'self,
/// An iterator that calls a function with a reference to each /// An iterator that calls a function with a reference to each
/// element before yielding it. /// element before yielding it.
pub struct Peek<'self, A, T> { pub struct Inspect<'self, A, T> {
priv iter: T, priv iter: T,
priv f: &'self fn(&A) priv f: &'self fn(&A)
} }
impl<'self, A, T> Peek<'self, A, T> { impl<'self, A, T> Inspect<'self, A, T> {
#[inline] #[inline]
fn do_peek(&self, elt: Option<A>) -> Option<A> { fn do_inspect(&self, elt: Option<A>) -> Option<A> {
match elt { match elt {
Some(ref a) => (self.f)(a), Some(ref a) => (self.f)(a),
None => () None => ()
@ -1346,11 +1400,11 @@ impl<'self, A, T> Peek<'self, A, T> {
} }
} }
impl<'self, A, T: Iterator<A>> Iterator<A> for Peek<'self, A, T> { impl<'self, A, T: Iterator<A>> Iterator<A> for Inspect<'self, A, T> {
#[inline] #[inline]
fn next(&mut self) -> Option<A> { fn next(&mut self) -> Option<A> {
let next = self.iter.next(); let next = self.iter.next();
self.do_peek(next) self.do_inspect(next)
} }
#[inline] #[inline]
@ -1359,15 +1413,17 @@ impl<'self, A, T: Iterator<A>> Iterator<A> for Peek<'self, A, T> {
} }
} }
impl<'self, A, T: DoubleEndedIterator<A>> DoubleEndedIterator<A> for Peek<'self, A, T> { impl<'self, A, T: DoubleEndedIterator<A>> DoubleEndedIterator<A>
for Inspect<'self, A, T> {
#[inline] #[inline]
fn next_back(&mut self) -> Option<A> { fn next_back(&mut self) -> Option<A> {
let next = self.iter.next_back(); let next = self.iter.next_back();
self.do_peek(next) self.do_inspect(next)
} }
} }
impl<'self, A, T: RandomAccessIterator<A>> RandomAccessIterator<A> for Peek<'self, A, T> { impl<'self, A, T: RandomAccessIterator<A>> RandomAccessIterator<A>
for Inspect<'self, A, T> {
#[inline] #[inline]
fn indexable(&self) -> uint { fn indexable(&self) -> uint {
self.iter.indexable() self.iter.indexable()
@ -1375,7 +1431,7 @@ impl<'self, A, T: RandomAccessIterator<A>> RandomAccessIterator<A> for Peek<'sel
#[inline] #[inline]
fn idx(&self, index: uint) -> Option<A> { fn idx(&self, index: uint) -> Option<A> {
self.do_peek(self.iter.idx(index)) self.do_inspect(self.iter.idx(index))
} }
} }
@ -1566,6 +1622,24 @@ mod tests {
} }
} }
#[test]
fn test_iterator_peekable() {
let xs = ~[0u, 1, 2, 3, 4, 5];
let mut it = xs.iter().map(|&x|x).peekable();
assert_eq!(it.peek().unwrap(), &0);
assert_eq!(it.next().unwrap(), 0);
assert_eq!(it.next().unwrap(), 1);
assert_eq!(it.next().unwrap(), 2);
assert_eq!(it.peek().unwrap(), &3);
assert_eq!(it.peek().unwrap(), &3);
assert_eq!(it.next().unwrap(), 3);
assert_eq!(it.next().unwrap(), 4);
assert_eq!(it.peek().unwrap(), &5);
assert_eq!(it.next().unwrap(), 5);
assert!(it.peek().is_none());
assert!(it.next().is_none());
}
#[test] #[test]
fn test_iterator_take_while() { fn test_iterator_take_while() {
let xs = [0u, 1, 2, 3, 5, 13, 15, 16, 17, 19]; let xs = [0u, 1, 2, 3, 5, 13, 15, 16, 17, 19];
@ -1651,13 +1725,13 @@ mod tests {
} }
#[test] #[test]
fn test_peek() { fn test_inspect() {
let xs = [1u, 2, 3, 4]; let xs = [1u, 2, 3, 4];
let mut n = 0; let mut n = 0;
let ys = xs.iter() let ys = xs.iter()
.map(|&x| x) .map(|&x| x)
.peek(|_| n += 1) .inspect(|_| n += 1)
.collect::<~[uint]>(); .collect::<~[uint]>();
assert_eq!(n, xs.len()); assert_eq!(n, xs.len());
@ -2011,11 +2085,11 @@ mod tests {
} }
#[test] #[test]
fn test_random_access_peek() { fn test_random_access_inspect() {
let xs = [1, 2, 3, 4, 5]; let xs = [1, 2, 3, 4, 5];
// test .map and .peek that don't implement Clone // test .map and .inspect that don't implement Clone
let it = xs.iter().peek(|_| {}); let it = xs.iter().inspect(|_| {});
assert_eq!(xs.len(), it.indexable()); assert_eq!(xs.len(), it.indexable());
for (i, elt) in xs.iter().enumerate() { for (i, elt) in xs.iter().enumerate() {
assert_eq!(Some(elt), it.idx(i)); assert_eq!(Some(elt), it.idx(i));
@ -2027,7 +2101,6 @@ mod tests {
fn test_random_access_map() { fn test_random_access_map() {
let xs = [1, 2, 3, 4, 5]; let xs = [1, 2, 3, 4, 5];
// test .map and .peek that don't implement Clone
let it = xs.iter().map(|x| *x); let it = xs.iter().map(|x| *x);
assert_eq!(xs.len(), it.indexable()); assert_eq!(xs.len(), it.indexable());
for (i, elt) in xs.iter().enumerate() { for (i, elt) in xs.iter().enumerate() {