rust/src/lib/either.rs

import option;
import option::some;
import option::none;

tag t[T, U] { left(T); right(U); }

fn either[T, U, V](f_left: &block(&T) -> V, f_right: &block(&U) -> V,
                   value: &t[T, U]) -> V {
    alt value { left(l) { f_left(l) } right(r) { f_right(r) } }
}

fn lefts[T, U](eithers: &[t[T, U]]) -> [T] {
    let result: [T] = ~[];
    for elt: t[T, U] in eithers {
        alt elt { left(l) { result += ~[l] } _ {/* fallthrough */ } }
    }
    ret result;
}

fn rights[T, U](eithers: &[t[T, U]]) -> [U] {
    let result: [U] = ~[];
    for elt: t[T, U] in eithers {
        alt elt { right(r) { result += ~[r] } _ {/* fallthrough */ } }
    }
    ret result;
}

fn partition[T, U](eithers: &[t[T, U]]) -> {lefts: [T], rights: [U]} {
    let lefts: [T] = ~[];
    let rights: [U] = ~[];
    for elt: t[T, U] in eithers {
        alt elt { left(l) { lefts += ~[l] } right(r) { rights += ~[r] } }
    }
    ret {lefts: lefts, rights: rights};
}
//
// 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:
//