(* Title: ZF/Coind/Language.thy Author: Jacob Frost, Cambridge University Computer Laboratory Copyright 1995 University of Cambridge *) theory Language imports ZF begin text‹these really can't be definitions without losing the abstraction› axiomatization Const :: i and (* Abstract type of constants *) c_app :: "[i,i] ⇒ i" (* Abstract constructor for fun application*) where constNEE: "c ∈ Const ⟹ c ≠ 0" and c_appI: "⟦c1 ∈ Const; c2 ∈ Const⟧ ⟹ c_app(c1,c2) ∈ Const" consts Exp :: i (* Datatype of expressions *) ExVar :: i (* Abstract type of variables *) datatype "Exp" = e_const ("c ∈ Const") | e_var ("x ∈ ExVar") | e_fn ("x ∈ ExVar","e ∈ Exp") | e_fix ("x1 ∈ ExVar","x2 ∈ ExVar","e ∈ Exp") | e_app ("e1 ∈ Exp","e2 ∈ Exp") end