91 lines
2.3 KiB
Rust
91 lines
2.3 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](vec[T] v) -> list[T] {
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auto 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 (T item 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](&list[T] ls_, &U u, fn(&T, &U) -> U f) -> U {
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let U accum = u;
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auto ls = ls_;
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while (true) {
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alt (ls) {
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case (cons(?hd, ?tl)) { accum = f(hd, accum); ls = *tl; }
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case (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](&list[T] ls_, fn(&T) -> option::t[U] f) -> option::t[U] {
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auto ls = ls_;
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while (true) {
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alt (ls) {
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case (cons(?hd, ?tl)) {
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alt (f(hd)) {
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case (none) { ls = *tl; }
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case (some(?rs)) { ret some(rs); }
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}
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}
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case (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](&list[T] ls_, &T elt) -> bool {
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auto ls = ls_;
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while (true) {
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alt (ls) {
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case (cons(?hd, ?tl)) {
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if (elt == hd) { ret true; } else { ls = *tl; }
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}
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case (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](&list[T] ls) -> uint {
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fn count[T](&T t, &uint u) -> 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](&list[T] ls) -> list[T] {
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alt (ls) { case (cons(_, ?tl)) { ret *tl; } }
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}
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fn car[T](&list[T] ls) -> T { alt (ls) { case (cons(?hd, _)) { ret hd; } } }
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fn append[T](&list[T] l, &list[T] m) -> list[T] {
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alt (l) {
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case (nil) { ret m; }
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case (cons(?x, ?xs)) {
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let list[T] rest = 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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