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type option[T] = tag(none(), some(T));
type box[T] = tup(@T);
type boxo[T] = option[box[T]];
type boxm[T] = tup(mutable @T);
type boxmo[T] = option[boxm[T]];
type map[T, U] = fn(&T) -> U;
fn option_map[T, U](map[T, U] f, &option[T] opt) -> option[U] {
alt (opt) {
case (some[T](x)) {
ret some[U](f[T, U](x));
}
case (none[T]()) {
ret none[U]();
}
}
}
fn unbox[T](&box[T] b) -> T {
ret b._0;
}
fn unboxm[T](&boxm[T] b) -> T {
ret b._0;
}
fn unboxo[T](boxo[T] b) -> option[T] {
// Pending issue #90, no need to alias the function item in order to pass
// it as an arg.
let map[box[T], T] f = unbox[T];
be option_map[box[T], T](f, b);
}
fn unboxmo[T](boxmo[T] b) -> option[T] {
// Issue #90, as above
let map[boxm[T], T] f = unboxm[T];
be option_map[boxm[T], T](f, b);
}
fn id[T](T x) -> T {
ret x;
}
type rational = rec(int num, int den);
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