author | wenzelm |
Tue, 16 Oct 2007 17:07:40 +0200 | |
changeset 25056 | 743f3603ba8b |
parent 24628 | 33137422d7fd |
child 25182 | 64e3f45dc6f4 |
permissions | -rw-r--r-- |
module Codegen where { import qualified Nat; class Null a where { nulla :: a; }; heada :: (Codegen.Null b) => [b] -> b; heada (x : xs) = x; heada [] = Codegen.nulla; null_option :: Maybe a; null_option = Nothing; instance Codegen.Null (Maybe a) where { nulla = Codegen.null_option; }; dummy :: Maybe Nat.Nat; dummy = Codegen.heada [Just (Nat.Suc Nat.Zero_nat), Nothing]; }