Struct yz_string_utils::AdvanPeekIter [−][src]
pub struct AdvanPeekIter<I> where
I: Iterator, { /* fields omitted */ }Implementations
like take_while, but doesn’t consume the first non-matching line by utilizing Peekable
Methods from Deref<Target = Peekable<I>>
Returns a reference to the next() value without advancing the iterator.
Like next, if there is a value, it is wrapped in a Some(T).
But if the iteration is over, None is returned.
Because peek() returns a reference, and many iterators iterate over
references, there can be a possibly confusing situation where the
return value is a double reference. You can see this effect in the
examples below.
Examples
Basic usage:
let xs = [1, 2, 3];
let mut iter = xs.iter().peekable();
// peek() lets us see into the future
assert_eq!(iter.peek(), Some(&&1));
assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
// The iterator does not advance even if we `peek` multiple times
assert_eq!(iter.peek(), Some(&&3));
assert_eq!(iter.peek(), Some(&&3));
assert_eq!(iter.next(), Some(&3));
// After the iterator is finished, so is `peek()`
assert_eq!(iter.peek(), None);
assert_eq!(iter.next(), None);Returns a mutable reference to the next() value without advancing the iterator.
Like next, if there is a value, it is wrapped in a Some(T).
But if the iteration is over, None is returned.
Because peek_mut() returns a reference, and many iterators iterate over
references, there can be a possibly confusing situation where the
return value is a double reference. You can see this effect in the examples
below.
Examples
Basic usage:
let mut iter = [1, 2, 3].iter().peekable();
// Like with `peek()`, we can see into the future without advancing the iterator.
assert_eq!(iter.peek_mut(), Some(&mut &1));
assert_eq!(iter.peek_mut(), Some(&mut &1));
assert_eq!(iter.next(), Some(&1));
// Peek into the iterator and set the value behind the mutable reference.
if let Some(p) = iter.peek_mut() {
assert_eq!(*p, &2);
*p = &5;
}
// The value we put in reappears as the iterator continues.
assert_eq!(iter.collect::<Vec<_>>(), vec![&5, &3]);Consume and return the next value of this iterator if a condition is true.
If func returns true for the next value of this iterator, consume and return it.
Otherwise, return None.
Examples
Consume a number if it’s equal to 0.
let mut iter = (0..5).peekable();
// The first item of the iterator is 0; consume it.
assert_eq!(iter.next_if(|&x| x == 0), Some(0));
// The next item returned is now 1, so `consume` will return `false`.
assert_eq!(iter.next_if(|&x| x == 0), None);
// `next_if` saves the value of the next item if it was not equal to `expected`.
assert_eq!(iter.next(), Some(1));Consume any number less than 10.
let mut iter = (1..20).peekable();
// Consume all numbers less than 10
while iter.next_if(|&x| x < 10).is_some() {}
// The next value returned will be 10
assert_eq!(iter.next(), Some(10));Consume and return the next item if it is equal to expected.
Example
Consume a number if it’s equal to 0.
let mut iter = (0..5).peekable();
// The first item of the iterator is 0; consume it.
assert_eq!(iter.next_if_eq(&0), Some(0));
// The next item returned is now 1, so `consume` will return `false`.
assert_eq!(iter.next_if_eq(&0), None);
// `next_if_eq` saves the value of the next item if it was not equal to `expected`.
assert_eq!(iter.next(), Some(1));