8693943676
This removes the stacking of type parameters that occurs when invoking trait methods, and fixes all places in the standard library that were relying on it. It is somewhat awkward in places; I think we'll probably want something like the `Foo::<for T>::new()` syntax.
131 lines
3.3 KiB
Rust
131 lines
3.3 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A mutable, nullable memory location
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#[missing_doc];
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use cast::transmute_mut;
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use unstable::finally::Finally;
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use prelude::*;
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/*
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A dynamic, mutable location.
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Similar to a mutable option type, but friendlier.
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*/
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#[no_freeze]
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#[deriving(Clone, DeepClone, Eq)]
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#[allow(missing_doc)]
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pub struct Cell<T> {
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priv value: Option<T>
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}
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impl<T> Cell<T> {
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/// Creates a new full cell with the given value.
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pub fn new(value: T) -> Cell<T> {
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Cell { value: Some(value) }
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}
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/// Creates a new empty cell with no value inside.
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pub fn new_empty() -> Cell<T> {
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Cell { value: None }
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}
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/// Yields the value, failing if the cell is empty.
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pub fn take(&self) -> T {
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let this = unsafe { transmute_mut(self) };
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if this.is_empty() {
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fail!("attempt to take an empty cell");
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}
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this.value.take_unwrap()
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}
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/// Yields the value if the cell is full, or `None` if it is empty.
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pub fn take_opt(&self) -> Option<T> {
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let this = unsafe { transmute_mut(self) };
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this.value.take()
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}
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/// Returns the value, failing if the cell is full.
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pub fn put_back(&self, value: T) {
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let this = unsafe { transmute_mut(self) };
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if !this.is_empty() {
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fail!("attempt to put a value back into a full cell");
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}
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this.value = Some(value);
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}
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/// Returns true if the cell is empty and false if the cell is full.
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pub fn is_empty(&self) -> bool {
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self.value.is_none()
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}
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/// Calls a closure with a reference to the value.
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pub fn with_ref<R>(&self, op: &fn(v: &T) -> R) -> R {
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do self.with_mut_ref |ptr| { op(ptr) }
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}
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/// Calls a closure with a mutable reference to the value.
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pub fn with_mut_ref<R>(&self, op: &fn(v: &mut T) -> R) -> R {
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let mut v = Some(self.take());
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do (|| {
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op(v.get_mut_ref())
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}).finally {
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self.put_back(v.take_unwrap());
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}
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}
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}
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#[test]
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fn test_basic() {
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let value_cell = Cell::new(~10);
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assert!(!value_cell.is_empty());
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let value = value_cell.take();
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assert!(value == ~10);
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assert!(value_cell.is_empty());
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value_cell.put_back(value);
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assert!(!value_cell.is_empty());
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}
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#[test]
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#[should_fail]
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fn test_take_empty() {
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let value_cell: Cell<~int> = Cell::new_empty();
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value_cell.take();
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}
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#[test]
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#[should_fail]
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fn test_put_back_non_empty() {
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let value_cell = Cell::new(~10);
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value_cell.put_back(~20);
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}
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#[test]
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fn test_with_ref() {
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let good = 6;
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let c = Cell::new(~[1, 2, 3, 4, 5, 6]);
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let l = do c.with_ref() |v| { v.len() };
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assert_eq!(l, good);
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}
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#[test]
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fn test_with_mut_ref() {
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let good = ~[1, 2, 3];
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let v = ~[1, 2];
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let c = Cell::new(v);
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do c.with_mut_ref() |v| { v.push(3); }
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let v = c.take();
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assert_eq!(v, good);
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}
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