(* Title: Pure/Proof/proofchecker.ML
ID: $Id$
Author: Stefan Berghofer, TU Muenchen
Simple proof checker based only on the core inference rules
of Isabelle/Pure.
*)
signature PROOF_CHECKER =
sig
val thm_of_proof : theory -> Proofterm.proof -> thm
end;
structure ProofChecker : PROOF_CHECKER =
struct
open Proofterm;
(***** construct a theorem out of a proof term *****)
fun lookup_thm thy =
let val tab = fold_rev Symtab.update (PureThy.all_thms_of thy) Symtab.empty
in
(fn s => case Symtab.lookup tab s of
NONE => error ("Unknown theorem " ^ quote s)
| SOME thm => thm)
end;
val beta_eta_convert =
Drule.fconv_rule Drule.beta_eta_conversion;
fun thm_of_proof thy prf =
let
val names = add_prf_names ([], prf);
val sg = sign_of thy;
val lookup = lookup_thm thy;
fun thm_of_atom thm Ts =
let
val tvars = term_tvars (Thm.full_prop_of thm);
val (thm', fmap) = Thm.varifyT' [] thm;
val ctye = map (pairself (Thm.ctyp_of sg))
(map TVar tvars @ map (fn ((_, S), ixn) => TVar (ixn, S)) fmap ~~ Ts)
in
Thm.instantiate (ctye, []) (forall_intr_vars (forall_intr_frees thm'))
end;
fun thm_of _ _ (PThm ((name, _), _, prop', SOME Ts)) =
let
val thm = Drule.implies_intr_hyps (lookup name);
val {prop, ...} = rep_thm thm;
val _ = if prop aconv prop' then () else
error ("Duplicate use of theorem name " ^ quote name ^ "\n" ^
Sign.string_of_term sg prop ^ "\n\n" ^
Sign.string_of_term sg prop');
in thm_of_atom thm Ts end
| thm_of _ _ (PAxm (name, _, SOME Ts)) =
thm_of_atom (get_axiom thy name) Ts
| thm_of _ Hs (PBound i) = List.nth (Hs, i)
| thm_of vs Hs (Abst (s, SOME T, prf)) =
let
val x = variant (names @ map fst vs) s;
val thm = thm_of ((x, T) :: vs) Hs prf
in
Thm.forall_intr (Thm.cterm_of sg (Free (x, T))) thm
end
| thm_of vs Hs (prf % SOME t) =
let
val thm = thm_of vs Hs prf
val ct = Thm.cterm_of sg (Term.subst_bounds (map Free vs, t))
in Thm.forall_elim ct thm end
| thm_of vs Hs (AbsP (s, SOME t, prf)) =
let
val ct = Thm.cterm_of sg (Term.subst_bounds (map Free vs, t));
val thm = thm_of vs (Thm.assume ct :: Hs) prf
in
Thm.implies_intr ct thm
end
| thm_of vs Hs (prf %% prf') =
let
val thm = beta_eta_convert (thm_of vs Hs prf);
val thm' = beta_eta_convert (thm_of vs Hs prf')
in
Thm.implies_elim thm thm'
end
| thm_of _ _ (Hyp t) = Thm.assume (Thm.cterm_of sg t)
| thm_of _ _ _ = error "thm_of_proof: partial proof term";
in beta_eta_convert (thm_of [] [] prf) end;
end;