47 lines
940 B
Rust
47 lines
940 B
Rust
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/**
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* Miscellaneous helpers for common patterns.
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*/
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/**
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* Swap the values at two mutable locations of the same type, without
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* deinitialising or copying either one.
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*/
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fn swap<T>(x: &mut T, y: &mut T) {
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*x <-> *y;
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}
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/**
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* Replace the value at a mutable location with a new one, returning the old
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* value, without deinitialising or copying either one.
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*/
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fn replace<T>(dest: &mut T, +src: T) -> T {
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let mut tmp = src;
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swap(dest, &mut tmp);
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tmp
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}
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/// A non-copyable dummy type.
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class noncopyable {
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i: ();
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new() { self.i = (); }
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drop { }
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}
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mod tests {
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#[test]
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fn test_swap() {
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let mut x = 31337;
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let mut y = 42;
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swap(&mut x, &mut y);
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assert x == 42;
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assert y == 31337;
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}
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#[test]
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fn test_replace() {
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let mut x = some(noncopyable());
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let y = replace(&mut x, none);
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assert x.is_none();
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assert y.is_some();
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}
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}
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