aef1e10eba
Fix a laundry list of warnings involving unused imports that glutted up compilation output. There are more, but there seems to be some false positives (where 'remedy' appears to break the build), but this particular set of fixes seems safe.
125 lines
3 KiB
Rust
125 lines
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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use cast::transmute_mut;
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use prelude::*;
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use util::replace;
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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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#[mutable]
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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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/// Creates a new full cell with the given value.
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pub fn Cell<T>(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 empty_cell<T>() -> Cell<T> {
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Cell { value: None }
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}
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pub impl<T> Cell<T> {
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/// Yields the value, failing if the cell is empty.
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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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replace(&mut this.value, None).unwrap()
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}
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/// Returns the value, failing if the cell is full.
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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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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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fn with_ref<R>(&self, op: &fn(v: &T) -> R) -> R {
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let v = self.take();
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let r = op(&v);
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self.put_back(v);
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r
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}
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// Calls a closure with a mutable reference to the value.
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fn with_mut_ref<R>(&self, op: &fn(v: &mut T) -> R) -> R {
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let mut v = self.take();
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let r = op(&mut v);
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self.put_back(v);
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r
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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(~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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#[ignore(cfg(windows))]
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fn test_take_empty() {
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let value_cell = empty_cell::<~int>();
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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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#[ignore(cfg(windows))]
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fn test_put_back_non_empty() {
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let value_cell = Cell(~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(~[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(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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