author | haftmann |
Thu, 26 Apr 2007 13:32:55 +0200 | |
changeset 22798 | e3962371f568 |
parent 22751 | 1bfd75c1f232 |
child 24421 | acfb2413faa3 |
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 b) where { nulla = Codegen.null_option; }; dummy :: Maybe Nat.Nat; dummy = Codegen.heada [Just (Nat.Suc Nat.Zero_nat), Nothing]; }