27 lines
643 B
Rust
27 lines
643 B
Rust
type option[T] = tag(none(), some(T));
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type operator[T, U] = fn(&T) -> U;
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fn option_map[T, U](&operator[T, U] f, &option[T] opt) -> option[U] {
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alt (opt) {
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case (some[T](x)) {
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ret some[U](f(x));
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}
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case (none[T]()) {
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ret none[U]();
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}
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}
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}
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fn id[T](&T x) -> T {
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ret x;
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}
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/* FIXME (issue #141): See test/run-pass/constrained-type.rs. Uncomment
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* the constraint once fixed. */
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type rational = rec(int num, int den); // : _int.positive(*.den);
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fn rational_leq(&rational x, &rational y) -> bool {
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// NB: Uses the fact that rationals have positive denominators WLOG.
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ret x.num * y.den <= y.num * x.den;
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}
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