90 lines
1.9 KiB
Rust
90 lines
1.9 KiB
Rust
import option::some;
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import option::none;
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tag list<T> { cons(T, @list<T>); nil; }
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fn from_vec<@T>(v: &[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: &block(&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: &block(&T) -> option::t<U>)
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-> 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. { break; }
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}
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}
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ret false;
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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(ls, 0u, count);
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}
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fn cdr<@T>(ls: &list<T>) -> list<T> {
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alt ls {
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cons(_, tl) { ret *tl; }
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nil. { fail "list empty" }
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}
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}
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fn car<@T>(ls: &list<T>) -> T {
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alt ls {
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cons(hd, _) { ret hd; }
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nil. { fail "list empty" }
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}
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}
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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 = append(*xs, m);
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ret cons(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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