rust/src/lib/option.rs

// lib/option::rs

tag t<@T> { none; some(T); }

fn get<@T>(opt: t<T>) -> T {
    alt opt { some(x) { x } none. { fail "option none" } }
}

fn map<@T, @U>(f: block(T) -> U, opt: t<T>) -> t<U> {
    alt opt { some(x) { some(f(x)) } none. { none } }
}

fn is_none<@T>(opt: t<T>) -> bool {
    alt opt { none. { true } some(_) { false } }
}

fn is_some<@T>(opt: t<T>) -> bool { !is_none(opt) }

fn from_maybe<@T>(def: T, opt: t<T>) -> T {
    alt opt { some(x) { x } none. { def } }
}

fn maybe<@T, @U>(def: U, f: block(T) -> U, opt: t<T>) -> U {
    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: block(T), opt: t<T>) {
    alt opt { none. {/* nothing */ } some(t) { f(t); } }
}

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// 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'";
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