doc-src/Codegen/Thy/examples/Example.hs
author wenzelm
Wed, 10 Jun 2009 11:28:39 +0200
changeset 31544 19b77b1de188
parent 31045 f0c7607bb295
child 31848 e5ab21d14974
permissions -rw-r--r--
updated generated files;

{-# OPTIONS_GHC -fglasgow-exts #-}

module Example where {


foldla :: forall a_1 b_1. (a_1 -> b_1 -> a_1) -> a_1 -> [b_1] -> a_1;
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;

}