{-# OPTIONS_GHC -fglasgow-exts #-}
module Example where {
foldla :: forall a b. (a -> b -> a) -> a -> [b] -> a;
foldla f a [] = a;
foldla f a (x : xs) = foldla f (f a x) xs;
rev :: forall a. [a] -> [a];
rev xs = foldla (\ xsa x -> x : xsa) [] xs;
list_case :: forall t a. t -> (a -> [a] -> t) -> [a] -> t;
list_case f1 f2 (a : list) = f2 a list;
list_case f1 f2 [] = f1;
data Queue a = AQueue [a] [a];
empty :: forall a. Queue a;
empty = AQueue [] [];
dequeue :: forall a. Queue a -> (Maybe a, Queue a);
dequeue (AQueue [] []) = (Nothing, AQueue [] []);
dequeue (AQueue xs (y : ys)) = (Just y, AQueue xs ys);
dequeue (AQueue (v : va) []) =
let {
(y : ys) = rev (v : va);
} in (Just y, AQueue [] ys);
enqueue :: forall a. a -> Queue a -> Queue a;
enqueue x (AQueue xs ys) = AQueue (x : xs) ys;
}