libcore: Add IteratorUtil::fold
, count
This commit is contained in:
parent
02945f1cb1
commit
b4cea351ba
1 changed files with 27 additions and 0 deletions
|
@ -50,6 +50,8 @@ pub trait IteratorUtil<A> {
|
|||
fn nth(&mut self, n: uint) -> A;
|
||||
fn first(&mut self) -> A;
|
||||
fn last(&mut self) -> A;
|
||||
fn fold<B>(&mut self, start: B, f: &fn(B, A) -> B) -> B;
|
||||
fn count(&mut self) -> uint;
|
||||
}
|
||||
|
||||
/// Iterator adaptors provided for every `Iterator` implementation. The adaptor objects are also
|
||||
|
@ -184,6 +186,23 @@ impl<A, T: Iterator<A>> IteratorUtil<A> for T {
|
|||
for self.advance |e| { elm = e; }
|
||||
return elm;
|
||||
}
|
||||
|
||||
/// Reduce an iterator to an accumulated value
|
||||
#[inline]
|
||||
fn fold<B>(&mut self, init: B, f: &fn(B, A) -> B) -> B {
|
||||
let mut accum = init;
|
||||
loop {
|
||||
match self.next() {
|
||||
Some(x) => { accum = f(accum, x); }
|
||||
None => { break; }
|
||||
}
|
||||
}
|
||||
return accum;
|
||||
}
|
||||
|
||||
/// Count the number of an iterator elemenrs
|
||||
#[inline(always)]
|
||||
fn count(&mut self) -> uint { self.fold(0, |cnt, _x| cnt + 1) }
|
||||
}
|
||||
|
||||
pub struct ChainIterator<T, U> {
|
||||
|
@ -648,4 +667,12 @@ mod tests {
|
|||
let v: &[uint] = &[];
|
||||
v.iter().last();
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn test_iterator_count() {
|
||||
let v = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
|
||||
assert_eq!(v.slice(0, 4).iter().count(), 4);
|
||||
assert_eq!(v.slice(0, 10).iter().count(), 10);
|
||||
assert_eq!(v.slice(0, 0).iter().count(), 0);
|
||||
}
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue