just one dedicated execution per document version -- NB: non-monotonicity of cancel always requires fresh update;
explicit terminate_execution;
tuned source structure;
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];
}