42 lines
1 KiB
Rust
42 lines
1 KiB
Rust
|
|
|
|
|
|
// lib/option::rs
|
|
tag t[T] { none; some(T); }
|
|
|
|
type operator[T, U] = fn(&T) -> U ;
|
|
|
|
fn get[T](opt: &t[T]) -> T { ret alt opt { some(x) { x } none. { fail } }; }
|
|
|
|
fn map[T, U](f: &operator[T, U], opt: &t[T]) -> t[U] {
|
|
ret alt opt { some(x) { some[U](f(x)) } none. { none[U] } };
|
|
}
|
|
|
|
fn is_none[T](opt: &t[T]) -> bool {
|
|
ret alt opt { none. { true } some(_) { false } };
|
|
}
|
|
|
|
fn is_some[T](opt: &t[T]) -> bool { ret !is_none(opt); }
|
|
|
|
fn from_maybe[T](def: &T, opt: &t[T]) -> T {
|
|
let f = bind util::id[T](_);
|
|
ret maybe[T, T](def, f, opt);
|
|
}
|
|
|
|
fn maybe[T, U](def: &U, f: fn(&T) -> U , opt: &t[T]) -> U {
|
|
ret alt opt { none. { def } some(t) { f(t) } };
|
|
}
|
|
|
|
|
|
// Can be defined in terms of the above when/if we have const bind.
|
|
fn may[T](f: fn(&T) , opt: &t[T]) {
|
|
alt opt { none. {/* nothing */ } 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:
|