| void main() { |
| List<int> list = [1, 2, 3]; |
| print(subs(list)); |
| print(perms(list)); |
| print(equals(list, list)); |
| } |
| |
| List<List<A>> subs<A>(List<A> list) => switch (list) { |
| [] => [], |
| [var x, ...var xs] => [ |
| for (var ys in subs(xs)) ...[ |
| [x] + ys, |
| ys |
| ], |
| [x] |
| ], |
| }; |
| |
| List<List<A>> perms<A>(List<A> list) => switch (list) { |
| [] || [_] => [list], |
| [var x, ...var xs] => [ |
| for (var i = 0; i < list.length; i++) |
| for (var perm in perms(xs)) [...perm.take(i), x, ...perm.skip(i)] |
| ], |
| }; |
| |
| bool equals<A>(List<A> a, List<A> b) => switch ((a, b)) { |
| ([], []) => true, |
| ([_, ...], []) => false, |
| ([], [_, ...]) => false, |
| ([var l, ...var ls], [var r, ...var rs]) => l == r && equals(ls, rs), |
| }; |