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// lib/option::rs
tag t[T] { none; some(T); }
type operator[T, U] = fn(&T) -> U ;
fn get[T](&t[T] opt) -> T {
ret alt (opt) { case (some(?x)) { x } case (none) { fail } };
}
fn map[T, U](&operator[T, U] f, &t[T] opt) -> t[U] {
ret alt (opt) {
case (some(?x)) { some[U](f(x)) }
case (none) { none[U] }
};
}
fn is_none[T](&t[T] opt) -> bool {
ret alt (opt) { case (none) { true } case (some(_)) { false } };
}
fn is_some[T](&t[T] opt) -> bool {
ret !is_none(opt);
}
fn from_maybe[T](&T def, &t[T] opt) -> T {
auto f = bind util::id[T](_);
ret maybe[T, T](def, f, opt);
}
fn maybe[T, U](&U def, fn(&T) -> U f, &t[T] opt) -> U {
ret alt (opt) { case (none) { def } case (some(?t)) { f(t) } };
}
// Can be defined in terms of the above when/if we have const bind.
fn may[T](fn(&T) f, &t[T] opt) {
alt (opt) { case (none) {/* nothing */ } case (some(?t)) { f(t); } }
}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
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