Theory Ctr_Sugar

(*  Title:      HOL/Ctr_Sugar.thy
    Author:     Jasmin Blanchette, TU Muenchen
    Author:     Dmitriy Traytel, TU Muenchen
    Copyright   2012, 2013

Wrapping existing freely generated type's constructors.
*)

header {* Wrapping Existing Freely Generated Type's Constructors *}

theory Ctr_Sugar
imports HOL
keywords
  "print_case_translations" :: diag and
  "free_constructors" :: thy_goal
begin

consts
  case_guard :: "bool => 'a => ('a => 'b) => 'b"
  case_nil :: "'a => 'b"
  case_cons :: "('a => 'b) => ('a => 'b) => 'a => 'b"
  case_elem :: "'a => 'b => 'a => 'b"
  case_abs :: "('c => 'b) => 'b"

declare [[coercion_args case_guard - + -]]
declare [[coercion_args case_cons - -]]
declare [[coercion_args case_abs -]]
declare [[coercion_args case_elem - +]]

ML_file "Tools/Ctr_Sugar/case_translation.ML"

lemma iffI_np: "[|x ==> ¬ y; ¬ x ==> y|] ==> ¬ x <-> y"
by (erule iffI) (erule contrapos_pn)

lemma iff_contradict:
"¬ P ==> P <-> Q ==> Q ==> R"
"¬ Q ==> P <-> Q ==> P ==> R"
by blast+

ML_file "Tools/Ctr_Sugar/ctr_sugar_util.ML"
ML_file "Tools/Ctr_Sugar/ctr_sugar_tactics.ML"
ML_file "Tools/Ctr_Sugar/ctr_sugar_code.ML"
ML_file "Tools/Ctr_Sugar/ctr_sugar.ML"

end