rust/src/lib/list.rs

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import option::some;
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
// a reverse vector iterator. Unfortunately generic iterators seem not to
// work yet.
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for item: T in ivec::reversed(v) { l = cons[T](item, @l); }
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ret l;
}
fn foldl[@T, @U](ls_: &list[T], u: &U, f: &block(&T, &U) -> U ) -> U {
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let accum: U = u;
let ls = ls_;
while true {
alt ls {
cons(hd, tl) { accum = f(hd, accum); ls = *tl; }
nil. { break; }
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}
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}
ret accum;
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}
fn find[@T, @U](ls_: &list[T], f: &block(&T) -> option::t[U])
-> option::t[U] {
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let ls = ls_;
while true {
alt ls {
cons(hd, tl) {
alt f(hd) { none. { ls = *tl; } some(rs) { ret some(rs); } }
}
nil. { break; }
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}
}
ret none;
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}
fn has[@T](ls_: &list[T], elt: &T) -> bool {
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let ls = ls_;
while true {
alt ls {
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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ret false;
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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] {
alt ls {
cons(_, tl) { ret *tl; }
nil. { fail "list empty" }
}
}
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fn car[@T](ls: &list[T]) -> T {
alt ls {
cons(hd, _) { ret hd; }
nil. { fail "list empty" }
}
}
fn append[@T](l: &list[T], m: &list[T]) -> list[T] {
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alt l {
nil. { ret m; }
cons(x, xs) {
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let rest = append(*xs, m);
ret cons(x, @rest);
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}
}
}
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// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End: