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Make list.find return an option of different type than the list element.

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This commit is contained in:
Graydon Hoare 2010-10-18 16:02:59 -07:00
parent 67d4427345
commit 68321b0de8
1 changed files with 7 additions and 7 deletions
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14
src/lib/list.rs
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@ -26,23 +26,23 @@ fn foldl[T,U](&list[T] ls, U u, fn(&T t, U u) -> U f) -> U {
} }
} }
fn find[T](&list[T] ls, fn find[T,U](&list[T] ls,
(fn(&T) -> option[T]) f) -> option[T] { (fn(&T) -> option[U]) f) -> option[U] {
alt(ls) { alt(ls) {
case (cons[T](?hd, ?tl)) { case (cons[T](?hd, ?tl)) {
alt (f(hd)) { alt (f(hd)) {
case (none[T]) { case (none[U]) {
// FIXME: should use 'be' here, not 'ret'. But parametric tail // FIXME: should use 'be' here, not 'ret'. But parametric tail
// calls currently don't work. // calls currently don't work.
ret find[T](*tl, f); ret find[T,U](*tl, f);
} }
case (some[T](?res)) { case (some[U](?res)) {
ret some[T](res); ret some[U](res);
} }
} }
} }
case (nil[T]) { case (nil[T]) {
ret none[T]; ret none[U];
} }
} }
} }