(* Title: HOL/ex/Multiquote.thy
Author: Markus Wenzel, TU Muenchen
*)
section \<open>Multiple nested quotations and anti-quotations\<close>
theory Multiquote
imports Main
begin
text \<open>
Multiple nested quotations and anti-quotations -- basically a
generalized version of de-Bruijn representation.
\<close>
syntax
"_quote" :: "'b \<Rightarrow> ('a \<Rightarrow> 'b)" ("\<guillemotleft>_\<guillemotright>" [0] 1000)
"_antiquote" :: "('a \<Rightarrow> 'b) \<Rightarrow> 'b" ("\<acute>_" [1000] 1000)
parse_translation \<open>
let
fun antiquote_tr i (Const (\<^syntax_const>\<open>_antiquote\<close>, _) $
(t as Const (\<^syntax_const>\<open>_antiquote\<close>, _) $ _)) = skip_antiquote_tr i t
| antiquote_tr i (Const (\<^syntax_const>\<open>_antiquote\<close>, _) $ 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>\<open>_antiquote\<close>, _)) $ 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>\<open>_quote\<close>, K quote_tr)] end
\<close>
text \<open>basic examples\<close>
term "\<guillemotleft>a + b + c\<guillemotright>"
term "\<guillemotleft>a + b + c + \<acute>x + \<acute>y + 1\<guillemotright>"
term "\<guillemotleft>\<acute>(f w) + \<acute>x\<guillemotright>"
term "\<guillemotleft>f \<acute>x \<acute>y z\<guillemotright>"
text \<open>advanced examples\<close>
term "\<guillemotleft>\<guillemotleft>\<acute>\<acute>x + \<acute>y\<guillemotright>\<guillemotright>"
term "\<guillemotleft>\<guillemotleft>\<acute>\<acute>x + \<acute>y\<guillemotright> \<circ> \<acute>f\<guillemotright>"
term "\<guillemotleft>\<acute>(f \<circ> \<acute>g)\<guillemotright>"
term "\<guillemotleft>\<guillemotleft>\<acute>\<acute>(f \<circ> \<acute>g)\<guillemotright>\<guillemotright>"
end