doc-src/Codegen/Thy/examples/Example.hs
author wenzelm
Sat, 17 Sep 2011 19:55:32 +0200
changeset 44956 01a1b3b3341f
parent 41185 d5f0e556ffd3
child 44970 52f809bc5402
permissions -rw-r--r--
raised default log level -- to avoid confusing warning about scala.tools.nsc.plugins.Plugin, which is mistaken as jEdit plugin;

{-# LANGUAGE ScopedTypeVariables #-}

module Example where {

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) = reverse (v : va);
  } in (Just y, AQueue [] ys);

enqueue :: forall a. a -> Queue a -> Queue a;
enqueue x (AQueue xs ys) = AQueue (x : xs) ys;

}