49 lines
1.1 KiB
Rust
49 lines
1.1 KiB
Rust
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// lib/option::rs
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tag t[T] { none; some(T); }
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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) { case (some(?x)) { x } case (none) { fail } };
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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(?x)) { some[U](f(x)) }
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case (none) { none[U] }
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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) { case (none) { true } case (some(_)) { false } };
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}
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fn is_some[T](&t[T] opt) -> bool {
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ret !is_none(opt);
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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) { case (none) { def } case (some(?t)) { f(t) } };
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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) { case (none) {/* nothing */ } case (some(?t)) { f(t); } }
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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 $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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