mirror of
https://github.com/rust-lang/rust.git
synced 2024-12-15 18:15:01 +00:00
52 lines
1.4 KiB
Rust
52 lines
1.4 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
// xfail-fast
|
|
|
|
trait vec_monad<A> {
|
|
fn bind<B>(&self, f: |&A| -> ~[B]) -> ~[B];
|
|
}
|
|
|
|
impl<A> vec_monad<A> for ~[A] {
|
|
fn bind<B>(&self, f: |&A| -> ~[B]) -> ~[B] {
|
|
let mut r = ~[];
|
|
for elt in self.iter() {
|
|
r.push_all_move(f(elt));
|
|
}
|
|
r
|
|
}
|
|
}
|
|
|
|
trait option_monad<A> {
|
|
fn bind<B>(&self, f: |&A| -> Option<B>) -> Option<B>;
|
|
}
|
|
|
|
impl<A> option_monad<A> for Option<A> {
|
|
fn bind<B>(&self, f: |&A| -> Option<B>) -> Option<B> {
|
|
match *self {
|
|
Some(ref a) => { f(a) }
|
|
None => { None }
|
|
}
|
|
}
|
|
}
|
|
|
|
fn transform(x: Option<int>) -> Option<~str> {
|
|
x.bind(|n| Some(*n + 1) ).bind(|n| Some(n.to_str()) )
|
|
}
|
|
|
|
pub fn main() {
|
|
assert_eq!(transform(Some(10)), Some(~"11"));
|
|
assert_eq!(transform(None), None);
|
|
assert!((~[~"hi"])
|
|
.bind(|x| ~[x.clone(), *x + "!"] )
|
|
.bind(|x| ~[x.clone(), *x + "?"] ) ==
|
|
~[~"hi", ~"hi?", ~"hi!", ~"hi!?"]);
|
|
}
|