88 lines
1.9 KiB
Rust
88 lines
1.9 KiB
Rust
// NB: transitionary, de-mode-ing.
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#[forbid(deprecated_mode)];
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#[forbid(deprecated_pattern)];
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use cmp::Eq;
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/**
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* Miscellaneous helpers for common patterns.
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*/
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/// The identity function.
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pure fn id<T>(+x: T) -> T { x }
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/// Ignores a value.
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pure fn ignore<T>(+_x: T) { }
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/// Sets `*ptr` to `new_value`, invokes `op()`, and then restores the
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/// original value of `*ptr`.
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#[inline(always)]
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fn with<T: copy, R>(
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ptr: &mut T,
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+new_value: T,
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op: &fn() -> R) -> R
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{
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// NDM: if swap operator were defined somewhat differently,
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// we wouldn't need to copy...
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let old_value = *ptr;
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*ptr = move new_value;
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let result = op();
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*ptr = move old_value;
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return move result;
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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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#[inline(always)]
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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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#[inline(always)]
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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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struct NonCopyable {
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i: (),
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drop { }
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}
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fn NonCopyable() -> NonCopyable { NonCopyable { i: () } }
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mod tests {
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#[test]
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fn identity_crisis() {
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// Writing a test for the identity function. How did it come to this?
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let x = ~[(5, false)];
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//FIXME #3387 assert x.eq(id(copy x));
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let y = copy x;
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assert x.eq(id(y));
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}
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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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