67 lines
1.3 KiB
Rust
67 lines
1.3 KiB
Rust
// lib/option::rs
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tag t[T] {
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none;
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some(T);
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}
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type operator[T, U] = fn(&T) -> U;
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fn get[T](&t[T] opt) -> T {
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ret alt (opt) {
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case (some[T](?x)) {
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x
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}
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case (none[T]) {
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fail
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}
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};
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}
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fn map[T, U](&operator[T, U] f, &t[T] opt) -> t[U] {
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ret alt (opt) {
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case (some[T](?x)) {
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some[U](f(x))
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}
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case (none[T]) {
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none[U]
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}
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};
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}
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fn is_none[T](&t[T] opt) -> bool {
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ret alt (opt) {
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case (none[T]) { true }
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case (some[T](_)) { false }
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};
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}
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fn from_maybe[T](&T def, &t[T] opt) -> T {
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auto f = bind util::id[T](_);
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ret maybe[T, T](def, f, opt);
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}
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fn maybe[T, U](&U def, fn(&T) -> U f, &t[T] opt) -> U {
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ret alt (opt) {
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case (none[T]) { def }
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case (some[T](?t)) { f(t) }
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};
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}
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// Can be defined in terms of the above when/if we have const bind.
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fn may[T](fn(&T) f, &t[T] opt) {
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alt (opt) {
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case (none[T]) { /* nothing */ }
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case (some[T](?t)) { f(t); }
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}
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}
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// Local Variables:
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// mode: rust;
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// compile-command: "make -k -C .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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