42 lines
1 KiB
Rust
42 lines
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](opt: &t[T]) -> T { ret alt opt { some(x) { x } none. { fail } }; }
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fn map[@T, @U](f: &operator[T, U], opt: &t[T]) -> t[U] {
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ret alt opt { some(x) { some[U](f(x)) } none. { none[U] } };
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}
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fn is_none[@T](opt: &t[T]) -> bool {
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ret alt opt { none. { true } some(_) { false } };
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}
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fn is_some[@T](opt: &t[T]) -> bool { ret !is_none(opt); }
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fn from_maybe[@T](def: &T, opt: &t[T]) -> T {
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let 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](def: &U, f: fn(&T) -> U , opt: &t[T]) -> U {
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ret alt opt { none. { def } 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](f: fn(&T) , opt: &t[T]) {
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alt opt { none. {/* nothing */ } 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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