84 lines
2.1 KiB
Rust
84 lines
2.1 KiB
Rust
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import option::some;
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import option::none;
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// FIXME: It would probably be more appealing to define this as
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// type list[T] = rec(T hd, option[@list[T]] tl), but at the moment
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// our recursion rules do not permit that.
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tag list[T] { cons(T, @list[T]); nil; }
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fn from_vec[@T](v: vec[T]) -> list[T] {
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let l = nil[T];
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// FIXME: This would be faster and more space efficient if it looped over
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// a reverse vector iterator. Unfortunately generic iterators seem not to
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// work yet.
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for item: T in vec::reversed(v) { l = cons[T](item, @l); }
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ret l;
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}
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fn foldl[@T, @U](ls_: &list[T], u: &U, f: fn(&T, &U) -> U ) -> U {
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let accum: U = u;
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let ls = ls_;
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while true {
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alt ls {
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cons(hd, tl) { accum = f(hd, accum); ls = *tl; }
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nil. { break; }
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}
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}
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ret accum;
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}
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fn find[@T, @U](ls_: &list[T], f: fn(&T) -> option::t[U] ) -> option::t[U] {
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let ls = ls_;
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while true {
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alt ls {
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cons(hd, tl) {
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alt f(hd) { none. { ls = *tl; } some(rs) { ret some(rs); } }
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}
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nil. { break; }
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}
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}
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ret none;
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}
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fn has[@T](ls_: &list[T], elt: &T) -> bool {
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let ls = ls_;
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while true {
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alt ls {
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cons(hd, tl) { if elt == hd { ret true; } else { ls = *tl; } }
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nil. { ret false; }
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}
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}
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ret false; // Typestate checker doesn't understand infinite loops
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}
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fn length[T](ls: &list[T]) -> uint {
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fn count[T](t: &T, u: &uint) -> uint { ret u + 1u; }
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ret foldl[T, uint](ls, 0u, bind count[T](_, _));
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}
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fn cdr[@T](ls: &list[T]) -> list[T] { alt ls { cons(_, tl) { ret *tl; } } }
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fn car[@T](ls: &list[T]) -> T { alt ls { cons(hd, _) { ret hd; } } }
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fn append[@T](l: &list[T], m: &list[T]) -> list[T] {
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alt l {
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nil. { ret m; }
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cons(x, xs) {
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let rest: list[T] = append[T](*xs, m);
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ret cons[T](x, @rest);
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}
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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 $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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