Quelle  Ctr_Sugar.thy

(*  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.
*)

section ‹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›

text ‹Coinduction method that avoids some boilerplate compared with coinduct.›

ML_file ‹Tools/coinduction.ML›

end