prune-lang 0.2.3

Prune is a constraint logic programming language with branching heuristic.
Documentation 
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datatype List[a] where
| Nil
| Cons(a, List[a])
end

function concat[a](xs: List[a], ys: List[a]) -> List[a]
begin
    match xs with
    | Nil => ys
    | Cons(head, tail) => Cons(head, concat(tail, ys))
    end
end

function rev_nat_list(n: Int) -> List[Int]
begin
    if n == 0 then Nil
    else Cons(n, rev_nat_list(n - 1))
end

function example(xs: List[Int], ys: List[Int])
begin
    guard concat(xs, ys) = rev_nat_list(100);
end

query example(depth_step=50, depth_limit=1000, answer_limit=101)