# Theory Multiquote

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theory Multiquote
imports Main
begin

    (*  Title:      HOL/ex/Multiquote.thy
        ID:         $Id: Multiquote.thy,v 1.13 2005/06/17 14:12:49 haftmann Exp $
        Author:     Markus Wenzel, TU Muenchen
    *)

    header {* Multiple nested quotations and anti-quotations *}

    theory Multiquote imports Main begin

    text {*
      Multiple nested quotations and anti-quotations -- basically a
      generalized version of de-Bruijn representation.
    *}

    syntax
      "_quote" :: "'b => ('a => 'b)"             ("«_»" [0] 1000)
      "_antiquote" :: "('a => 'b) => 'b"         ("´_" [1000] 1000)

    parse_translation {*
      let
        fun antiquote_tr i (Const ("_antiquote", _) $ (t as Const ("_antiquote", _) $ _)) =
              skip_antiquote_tr i t
          | antiquote_tr i (Const ("_antiquote", _) $ t) =
              antiquote_tr i t $ Bound i
          | antiquote_tr i (t $ u) = antiquote_tr i t $ antiquote_tr i u
          | antiquote_tr i (Abs (x, T, t)) = Abs (x, T, antiquote_tr (i + 1) t)
          | antiquote_tr _ a = a
        and skip_antiquote_tr i ((c as Const ("_antiquote", _)) $ t) =
              c $ skip_antiquote_tr i t
          | skip_antiquote_tr i t = antiquote_tr i t;

        fun quote_tr [t] = Abs ("s", dummyT, antiquote_tr 0 (Term.incr_boundvars 1 t))
          | quote_tr ts = raise TERM ("quote_tr", ts);
      in [("_quote", quote_tr)] end
    *}

    text {* basic examples *}
    term "«a + b + c»"
    term "«a + b + c + ´x + ´y + 1»"
    term "«´(f w) + ´x»"
    term "«f ´x ´y z»"

    text {* advanced examples *}
    term "««´´x + ´y»»"
    term "««´´x + ´y» o ´f»"
    term "«´(f o ´g)»"
    term "««´´(f o ´g)»»"

    end