author | haftmann |
Wed, 06 May 2009 16:01:05 +0200 | |
changeset 31045 | f0c7607bb295 |
parent 30226 | 2f4684e2ea95 |
permissions | -rw-r--r-- |
structure Nat = struct datatype nat = Suc of nat | Zero_nat; end; (*struct Nat*) structure Codegen = struct type 'a null = {null : 'a}; fun null (A_:'a null) = #null A_; fun head A_ (x :: xs) = x | head A_ [] = null A_; val null_option : 'a option = NONE; fun null_optiona () = {null = null_option} : ('a option) null; val dummy : Nat.nat option = head (null_optiona ()) [SOME (Nat.Suc Nat.Zero_nat), NONE]; end; (*struct Codegen*)