Theory HOL.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.
*)

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