(* Title: HOL/ex/Antiquote.thy
Author: Markus Wenzel, TU Muenchen
*)
section \<open>Antiquotations\<close>
theory Antiquote
imports Main
begin
text \<open>A simple example on quote / antiquote in higher-order abstract syntax.\<close>
definition var :: "'a \<Rightarrow> ('a \<Rightarrow> nat) \<Rightarrow> nat" ("VAR _" [1000] 999)
where "var x env = env x"
definition Expr :: "(('a \<Rightarrow> nat) \<Rightarrow> nat) \<Rightarrow> ('a \<Rightarrow> nat) \<Rightarrow> nat"
where "Expr exp env = exp env"
syntax
"_Expr" :: "'a \<Rightarrow> 'a" ("EXPR _" [1000] 999)
parse_translation
\<open>[Syntax_Trans.quote_antiquote_tr
@{syntax_const "_Expr"} @{const_syntax var} @{const_syntax Expr}]\<close>
print_translation
\<open>[Syntax_Trans.quote_antiquote_tr'
@{syntax_const "_Expr"} @{const_syntax var} @{const_syntax Expr}]\<close>
term "EXPR (a + b + c)"
term "EXPR (a + b + c + VAR x + VAR y + 1)"
term "EXPR (VAR (f w) + VAR x)"
term "Expr (\<lambda>env. env x)" -- \<open>improper\<close>
term "Expr (\<lambda>env. f env)"
term "Expr (\<lambda>env. f env + env x)" -- \<open>improper\<close>
term "Expr (\<lambda>env. f env y z)"
term "Expr (\<lambda>env. f env + g y env)"
term "Expr (\<lambda>env. f env + g env y + h a env z)"
end