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container -- update example to contain scope of closure borrow

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Niko Matsakis 2014-02-07 06:52:01 -05:00
parent 6f571a63a6
commit 0f5baad6ee
1 changed files with 19 additions and 13 deletions
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32
src/doc/guide-container.md
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@ -181,19 +181,25 @@ never call its underlying iterator again once `None` has been returned:
~~~
let xs = [1,2,3,4,5];
let mut calls = 0;
let it = xs.iter().scan((), |_, x| {
calls += 1;
if *x < 3 { Some(x) } else { None }});
// the iterator will only yield 1 and 2 before returning None
// If we were to call it 5 times, calls would end up as 5, despite only 2 values
// being yielded (and therefore 3 unique calls being made). The fuse() adaptor
// can fix this.
let mut it = it.fuse();
it.next();
it.next();
it.next();
it.next();
it.next();
{
let it = xs.iter().scan((), |_, x| {
calls += 1;
if *x < 3 { Some(x) } else { None }});
// the iterator will only yield 1 and 2 before returning None
// If we were to call it 5 times, calls would end up as 5, despite
// only 2 values being yielded (and therefore 3 unique calls being
// made). The fuse() adaptor can fix this.
let mut it = it.fuse();
it.next();
it.next();
it.next();
it.next();
it.next();
}
assert_eq!(calls, 3);
~~~