Advances iter, calling pred on each character.
If pred returns true, returns true and stops scanning. If pred never returns true, iter is set to limit if limit is non-null, otherwise to the end iterator.
a function to be called on each character
search limit
whether a match was found
Advances iter, calling pred on each character.
If pred returns true, returns true and stops scanning. If pred never returns true, iter is set to limit if limit is non-null, otherwise to the end iterator.