80 lines
1.8 KiB
Rust
80 lines
1.8 KiB
Rust
#[forbid(deprecated_mode)];
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#[forbid(deprecated_pattern)];
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/// A dynamic, mutable location.
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///
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/// Similar to a mutable option type, but friendlier.
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struct Cell<T> {
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mut value: Option<T>
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}
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/// Creates a new full cell with the given value.
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fn Cell<T>(+value: T) -> Cell<T> {
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Cell { value: Some(move value) }
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}
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fn empty_cell<T>() -> Cell<T> {
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Cell { value: None }
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}
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impl<T> Cell<T> {
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/// Yields the value, failing if the cell is empty.
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fn take() -> T {
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if self.is_empty() {
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fail ~"attempt to take an empty cell";
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}
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let mut value = None;
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value <-> self.value;
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return option::unwrap(move value);
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}
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/// Returns the value, failing if the cell is full.
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fn put_back(+value: T) {
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if !self.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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self.value = Some(move 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() -> 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>(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(move v);
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move 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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