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/*!
* A type representing values that may be computed concurrently and
* operations for working with them.
*
* # Example
*
* ~~~
* let delayed_fib = future::spawn {|| fib(5000) };
* make_a_sandwich();
* io::println(fmt!{"fib(5000) = %?", delayed_fib.get()})
* ~~~
*/
import either::either;
import pipes::recv;
export future;
export extensions;
export from_value;
export from_port;
export from_fn;
export get;
export with;
export spawn;
// for task.rs
export future_pipe;
#[doc = "The future type"]
enum future<A> = {
mut v: either<@A, fn@() -> A>
};
/// Methods on the `future` type
impl extensions<A:copy send> for future<A> {
fn get() -> A {
//! Get the value of the future
get(self)
}
fn with<B>(blk: fn(A) -> B) -> B {
//! Work with the value without copying it
with(self, blk)
}
}
fn from_value<A>(+val: A) -> future<A> {
/*!
* Create a future from a value
*
* The value is immediately available and calling `get` later will
* not block.
*/
future({
mut v: either::left(@val)
})
}
macro_rules! move{
{$x:expr} => { unsafe { let y <- *ptr::addr_of($x); y } }
}
fn from_port<A:send>(-port: future_pipe::client::waiting<A>) -> future<A> {
#[doc = "
Create a future from a port
The first time that the value is requested the task will block
waiting for the result to be received on the port.
"];
let port = ~mut some(port);
do from_fn |move port| {
let mut port_ = none;
port_ <-> *port;
let port = option::unwrap(port_);
alt recv(port) {
future_pipe::completed(data) { move!{data} }
}
}
}
fn from_fn<A>(f: fn@() -> A) -> future<A> {
/*!
* Create a future from a function.
*
* The first time that the value is requested it will be retreived by
* calling the function. Note that this function is a local
* function. It is not spawned into another task.
*/
future({
mut v: either::right(f)
})
}
fn spawn<A:send>(+blk: fn~() -> A) -> future<A> {
/*!
* Create a future from a unique closure.
*
* The closure will be run in a new task and its result used as the
* value of the future.
*/
from_port(pipes::spawn_service_recv(future_pipe::init, |ch| {
future_pipe::server::completed(ch, blk());
}))
}
fn get<A:copy>(future: future<A>) -> A {
//! Get the value of the future
do with(future) |v| { v }
}
fn with<A,B>(future: future<A>, blk: fn(A) -> B) -> B {
//! Work with the value without copying it
let v = alt copy future.v {
either::left(v) { v }
either::right(f) {
let v = @f();
future.v = either::left(v);
v
}
};
blk(*v)
}
proto! future_pipe {
waiting:recv<T:send> {
completed(T) -> !
}
}
#[test]
fn test_from_value() {
let f = from_value(~"snail");
assert get(f) == ~"snail";
}
#[test]
fn test_from_port() {
let (po, ch) = future_pipe::init();
future_pipe::server::completed(ch, ~"whale");
let f = from_port(po);
assert get(f) == ~"whale";
}
#[test]
fn test_from_fn() {
let f = fn@() -> ~str { ~"brail" };
let f = from_fn(f);
assert get(f) == ~"brail";
}
#[test]
fn test_iface_get() {
let f = from_value(~"fail");
assert f.get() == ~"fail";
}
#[test]
fn test_with() {
let f = from_value(~"nail");
assert with(f, |v| v) == ~"nail";
}
#[test]
fn test_iface_with() {
let f = from_value(~"kale");
assert f.with(|v| v) == ~"kale";
}
#[test]
fn test_spawn() {
let f = spawn(|| ~"bale");
assert get(f) == ~"bale";
}
#[test]
#[should_fail]
#[ignore(cfg(target_os = "win32"))]
fn test_futurefail() {
let f = spawn(|| fail);
let _x: ~str = get(f);
}
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