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import option::some;
import option::none;
// FIXME: It would probably be more appealing to define this as
// type list[T] = rec(T hd, option[@list[T]] tl), but at the moment
// our recursion rules do not permit that.
tag list[T] {
cons(T, @list[T]);
nil;
}
fn from_vec[T](vec[T] v) -> list[T] {
auto l = nil[T];
// 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.
for (T item in vec::reversed(v)) {
l = cons[T](item, @l);
}
ret l;
}
fn foldl[T,U](&list[T] ls, &U u, fn(&T t, &U u) -> U f) -> U {
alt(ls) {
case (cons(?hd, ?tl)) {
auto u_ = f(hd, u);
be foldl[T,U](*tl, u_, f);
}
case (nil) {
ret u;
}
}
}
fn find[T,U](&list[T] ls,
(fn(&T) -> option::t[U]) f) -> option::t[U] {
alt(ls) {
case (cons(?hd, ?tl)) {
alt (f(hd)) {
case (none) {
be find[T,U](*tl, f);
}
case (some(?res)) {
ret some[U](res);
}
}
}
case (nil) {
ret none[U];
}
}
}
fn has[T](&list[T] ls, &T elt) -> bool {
alt(ls) {
case (cons(?hd, ?tl)) {
if (elt == hd) {
ret true;
} else {
be has(*tl, elt);
}
}
case (nil) { ret false; }
}
}
fn length[T](&list[T] ls) -> uint {
fn count[T](&T t, &uint u) -> uint {
ret u + 1u;
}
ret foldl[T,uint](ls, 0u, bind count[T](_, _));
}
fn cdr[T](&list[T] ls) -> list[T] {
alt (ls) {
case (cons(_, ?tl)) {ret *tl;}
}
}
fn car[T](&list[T] ls) -> T {
alt (ls) {
case (cons(?hd, _)) {ret hd;}
}
}
fn append[T](&list[T] l, &list[T] m) -> list[T] {
alt (l) {
case (nil) {
ret m;
}
case (cons(?x, ?xs)) {
let list[T] rest = append[T](*xs, m);
ret cons[T](x, @rest);
}
}
}
// 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 .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
|
