| author | nipkow |
| Tue, 23 Jun 2009 12:59:44 +0200 | |
| changeset 31767 | b4c8d615bf5d |
| parent 30226 | 2f4684e2ea95 |
| permissions | -rw-r--r-- |
module Codegen where { import qualified Nat; class Null a where { nulla :: a; }; heada :: forall a. (Codegen.Null a) => [a] -> a; heada (x : xs) = x; heada [] = Codegen.nulla; null_option :: forall a. 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]; }