src/HOL/Proofs/ex/XML_Data.thy

proper syntax;

(*  Title:      HOL/Proofs/ex/XML_Data.thy
    Author:     Makarius
    Author:     Stefan Berghofer

XML data representation of proof terms.
*)

theory XML_Data
imports "~~/src/HOL/Isar_Examples/Drinker"
begin

subsection \<open>Export and re-import of global proof terms\<close>

ML \<open>
  fun export_proof thy thm =
    let
      val (_, prop) =
        Logic.unconstrainT (Thm.shyps_of thm)
          (Logic.list_implies (Thm.hyps_of thm, Thm.prop_of thm));
      val prf =
        Proofterm.proof_of (Proofterm.strip_thm (Thm.proof_body_of thm)) |>
        Reconstruct.reconstruct_proof thy prop |>
        Reconstruct.expand_proof thy [("", NONE)] |>
        Proofterm.rew_proof thy |>
        Proofterm.no_thm_proofs;
    in Proofterm.encode prf end;

  fun import_proof thy xml =
    let
      val prf = Proofterm.decode xml;
      val (prf', _) = Proofterm.freeze_thaw_prf prf;
    in Drule.export_without_context (Proof_Checker.thm_of_proof thy prf') end;
\<close>


subsection \<open>Examples\<close>

ML \<open>val thy1 = @{theory}\<close>

lemma ex: "A \<longrightarrow> A" ..

ML_val \<open>
  val xml = export_proof @{theory} @{thm ex};
  val thm = import_proof thy1 xml;
\<close>

ML_val \<open>
  val xml = export_proof @{theory} @{thm de_Morgan};
  val thm = import_proof thy1 xml;
\<close>

ML_val \<open>
  val xml = export_proof @{theory} @{thm Drinker's_Principle};
  val thm = import_proof thy1 xml;
\<close>

text \<open>Some fairly large proof:\<close>

ML_val \<open>
  val xml = export_proof @{theory} @{thm abs_less_iff};
  val thm = import_proof thy1 xml;
  @{assert} (size (YXML.string_of_body xml) > 1000000);
\<close>

end