Theory Multiquote

(*  Title:      HOL/ex/Multiquote.thy
    Author:     Markus Wenzel, TU Muenchen
*)

section ‹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 (\<^syntax_const>‹_antiquote›, _) $
          (t as Const (\<^syntax_const>‹_antiquote›, _) $ _)) = skip_antiquote_tr i t
      | antiquote_tr i (Const (\<^syntax_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 (\<^syntax_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 [(\<^syntax_const>‹_quote›, K 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» ∘ ´f»"
term "«´(f ∘ ´g)»"
term "««´´(f ∘ ´g)»»"

end