src/HOL/Integ/IntDef.ML

new files in Integ

(*  Title:      IntDef.ML
    ID:         $Id$
    Authors:    Lawrence C Paulson, Cambridge University Computer Laboratory
    Copyright   1993  University of Cambridge

The integers as equivalence classes over nat*nat.
*)


(*** Proving that intrel is an equivalence relation ***)

val eqa::eqb::prems = goal Arith.thy 
    "[| (x1::nat) + y2 = x2 + y1; x2 + y3 = x3 + y2 |] ==> \
\       x1 + y3 = x3 + y1";
by (res_inst_tac [("k1","x2")] (add_left_cancel RS iffD1) 1);
by (rtac (add_left_commute RS trans) 1);
by (stac eqb 1);
by (rtac (add_left_commute RS trans) 1);
by (stac eqa 1);
by (rtac (add_left_commute) 1);
qed "integ_trans_lemma";

(** Natural deduction for intrel **)

Goalw  [intrel_def] "[| x1+y2 = x2+y1|] ==> ((x1,y1),(x2,y2)): intrel";
by (Fast_tac 1);
qed "intrelI";

(*intrelE is hard to derive because fast_tac tries hyp_subst_tac so soon*)
Goalw [intrel_def]
  "p: intrel --> (EX x1 y1 x2 y2. \
\                  p = ((x1,y1),(x2,y2)) & x1+y2 = x2+y1)";
by (Fast_tac 1);
qed "intrelE_lemma";

val [major,minor] = Goal
  "[| p: intrel;  \
\     !!x1 y1 x2 y2. [| p = ((x1,y1),(x2,y2));  x1+y2 = x2+y1|] ==> Q |] \
\  ==> Q";
by (cut_facts_tac [major RS (intrelE_lemma RS mp)] 1);
by (REPEAT (eresolve_tac [asm_rl,exE,conjE,minor] 1));
qed "intrelE";

AddSIs [intrelI];
AddSEs [intrelE];

Goal "((x1,y1),(x2,y2)): intrel = (x1+y2 = x2+y1)";
by (Fast_tac 1);
qed "intrel_iff";

Goal "(x,x): intrel";
by (stac surjective_pairing 1 THEN rtac (refl RS intrelI) 1);
qed "intrel_refl";

Goalw [equiv_def, refl_def, sym_def, trans_def]
    "equiv {x::(nat*nat).True} intrel";
by (fast_tac (claset() addSIs [intrel_refl] 
                        addSEs [sym, integ_trans_lemma]) 1);
qed "equiv_intrel";

val equiv_intrel_iff =
    [TrueI, TrueI] MRS 
    ([CollectI, CollectI] MRS 
    (equiv_intrel RS eq_equiv_class_iff));

Goalw  [Integ_def,intrel_def,quotient_def] "intrel^^{(x,y)}:Integ";
by (Fast_tac 1);
qed "intrel_in_integ";

Goal "inj_on Abs_Integ Integ";
by (rtac inj_on_inverseI 1);
by (etac Abs_Integ_inverse 1);
qed "inj_on_Abs_Integ";

Addsimps [equiv_intrel_iff, inj_on_Abs_Integ RS inj_on_iff,
          intrel_iff, intrel_in_integ, Abs_Integ_inverse];

Goal "inj(Rep_Integ)";
by (rtac inj_inverseI 1);
by (rtac Rep_Integ_inverse 1);
qed "inj_Rep_Integ";


(** znat: the injection from nat to Integ **)

Goal "inj(znat)";
by (rtac injI 1);
by (rewtac znat_def);
by (dtac (inj_on_Abs_Integ RS inj_onD) 1);
by (REPEAT (rtac intrel_in_integ 1));
by (dtac eq_equiv_class 1);
by (rtac equiv_intrel 1);
by (Fast_tac 1);
by Safe_tac;
by (Asm_full_simp_tac 1);
qed "inj_znat";


(**** zminus: unary negation on Integ ****)

Goalw [congruent_def]
  "congruent intrel (%p. split (%x y. intrel^^{(y,x)}) p)";
by Safe_tac;
by (asm_simp_tac (simpset() addsimps add_ac) 1);
qed "zminus_congruent";


(*Resolve th against the corresponding facts for zminus*)
val zminus_ize = RSLIST [equiv_intrel, zminus_congruent];

Goalw [zminus_def]
      "- Abs_Integ(intrel^^{(x,y)}) = Abs_Integ(intrel ^^ {(y,x)})";
by (res_inst_tac [("f","Abs_Integ")] arg_cong 1);
by (simp_tac (simpset() addsimps 
   [intrel_in_integ RS Abs_Integ_inverse,zminus_ize UN_equiv_class]) 1);
qed "zminus";

(*by lcp*)
val [prem] = Goal "(!!x y. z = Abs_Integ(intrel^^{(x,y)}) ==> P) ==> P";
by (res_inst_tac [("x1","z")] 
    (rewrite_rule [Integ_def] Rep_Integ RS quotientE) 1);
by (dres_inst_tac [("f","Abs_Integ")] arg_cong 1);
by (res_inst_tac [("p","x")] PairE 1);
by (rtac prem 1);
by (asm_full_simp_tac (simpset() addsimps [Rep_Integ_inverse]) 1);
qed "eq_Abs_Integ";

Goal "- (- z) = (z::int)";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zminus]) 1);
qed "zminus_zminus";
Addsimps [zminus_zminus];

Goal "inj(uminus::int=>int)";
by (rtac injI 1);
by (dres_inst_tac [("f","uminus")] arg_cong 1);
by (Asm_full_simp_tac 1);
qed "inj_zminus";

Goalw [znat_def] "- ($# 0) = $# 0";
by (simp_tac (simpset() addsimps [zminus]) 1);
qed "zminus_nat0";

Addsimps [zminus_nat0];


(**** znegative: the test for negative integers ****)


Goalw [znegative_def, znat_def] "~ znegative($# n)";
by (Simp_tac 1);
by Safe_tac;
qed "not_znegative_znat";

Goalw [znegative_def, znat_def] "znegative(- $# Suc(n))";
by (simp_tac (simpset() addsimps [zminus]) 1);
qed "znegative_zminus_znat";

Addsimps [znegative_zminus_znat, not_znegative_znat]; 


(**** zadd: addition on Integ ****)

(** Congruence property for addition **)

Goalw [congruent2_def]
    "congruent2 intrel (%p1 p2.                  \
\         split (%x1 y1. split (%x2 y2. intrel^^{(x1+x2, y1+y2)}) p2) p1)";
(*Proof via congruent2_commuteI seems longer*)
by Safe_tac;
by (asm_simp_tac (simpset() addsimps [add_assoc]) 1);
(*The rest should be trivial, but rearranging terms is hard*)
by (res_inst_tac [("x1","x1a")] (add_left_commute RS ssubst) 1);
by (asm_simp_tac (simpset() addsimps [add_assoc RS sym]) 1);
qed "zadd_congruent2";

(*Resolve th against the corresponding facts for zadd*)
val zadd_ize = RSLIST [equiv_intrel, zadd_congruent2];

Goalw [zadd_def]
  "Abs_Integ(intrel^^{(x1,y1)}) + Abs_Integ(intrel^^{(x2,y2)}) = \
\  Abs_Integ(intrel^^{(x1+x2, y1+y2)})";
by (asm_simp_tac
    (simpset() addsimps [zadd_ize UN_equiv_class2]) 1);
qed "zadd";

Goal "- (z + w) = - z + - (w::int)";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zminus,zadd]) 1);
qed "zminus_zadd_distrib";
Addsimps [zminus_zadd_distrib];

Goal "(z::int) + w = w + z";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps (add_ac @ [zadd])) 1);
qed "zadd_commute";

Goal "((z1::int) + z2) + z3 = z1 + (z2 + z3)";
by (res_inst_tac [("z","z1")] eq_Abs_Integ 1);
by (res_inst_tac [("z","z2")] eq_Abs_Integ 1);
by (res_inst_tac [("z","z3")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zadd, add_assoc]) 1);
qed "zadd_assoc";

(*For AC rewriting*)
Goal "(x::int)+(y+z)=y+(x+z)";
by (rtac (zadd_commute RS trans) 1);
by (rtac (zadd_assoc RS trans) 1);
by (rtac (zadd_commute RS arg_cong) 1);
qed "zadd_left_commute";

(*Integer addition is an AC operator*)
val zadd_ac = [zadd_assoc,zadd_commute,zadd_left_commute];

Goalw [znat_def] "($#m) + ($#n) = $# (m + n)";
by (simp_tac (simpset() addsimps [zadd]) 1);
qed "add_znat";

Goal "$# (Suc m) = $# 1 + ($# m)";
by (simp_tac (simpset() addsimps [add_znat]) 1);
qed "znat_Suc";

Goalw [znat_def] "$# 0 + z = z";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zadd]) 1);
qed "zadd_nat0";

Goal "z + $# 0 = z";
by (rtac (zadd_commute RS trans) 1);
by (rtac zadd_nat0 1);
qed "zadd_nat0_right";

Goalw [znat_def] "z + (- z) = $# 0";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zminus, zadd, add_commute]) 1);
qed "zadd_zminus_inverse_nat";

Goal "(- z) + z = $# 0";
by (rtac (zadd_commute RS trans) 1);
by (rtac zadd_zminus_inverse_nat 1);
qed "zadd_zminus_inverse_nat2";

Addsimps [zadd_nat0, zadd_nat0_right,
	  zadd_zminus_inverse_nat, zadd_zminus_inverse_nat2];

Goal "z + (- z + w) = (w::int)";
by (asm_simp_tac (simpset() addsimps [zadd_assoc RS sym]) 1);
qed "zadd_zminus_cancel";

Goal "(-z) + (z + w) = (w::int)";
by (asm_simp_tac (simpset() addsimps [zadd_assoc RS sym]) 1);
qed "zminus_zadd_cancel";

Addsimps [zadd_zminus_cancel, zminus_zadd_cancel];


(** Lemmas **)

Goal "(z::int) + v = z' + v' ==> z + (v + w) = z' + (v' + w)";
by (asm_simp_tac (simpset() addsimps [zadd_assoc RS sym]) 1);
qed "zadd_assoc_cong";

Goal "(z::int) + (v + w) = v + (z + w)";
by (REPEAT (ares_tac [zadd_commute RS zadd_assoc_cong] 1));
qed "zadd_assoc_swap";


(*Need properties of subtraction?  Or use $- just as an abbreviation!*)

(**** zmult: multiplication on Integ ****)

(** Congruence property for multiplication **)

Goal "((k::nat) + l) + (m + n) = (k + m) + (n + l)";
by (simp_tac (simpset() addsimps add_ac) 1);
qed "zmult_congruent_lemma";

Goal "congruent2 intrel (%p1 p2.                 \
\               split (%x1 y1. split (%x2 y2.   \
\                   intrel^^{(x1*x2 + y1*y2, x1*y2 + y1*x2)}) p2) p1)";
by (rtac (equiv_intrel RS congruent2_commuteI) 1);
by (pair_tac "w" 2);
by (rename_tac "z1 z2" 2);
by Safe_tac;
by (rewtac split_def);
by (simp_tac (simpset() addsimps add_ac@mult_ac) 1);
by (asm_simp_tac (simpset() delsimps [equiv_intrel_iff]
                           addsimps add_ac@mult_ac) 1);
by (rtac (intrelI RS(equiv_intrel RS equiv_class_eq)) 1);
by (rtac (zmult_congruent_lemma RS trans) 1);
by (rtac (zmult_congruent_lemma RS trans RS sym) 1);
by (rtac (zmult_congruent_lemma RS trans RS sym) 1);
by (rtac (zmult_congruent_lemma RS trans RS sym) 1);
by (asm_simp_tac (simpset() addsimps [add_mult_distrib RS sym]) 1);
by (asm_simp_tac (simpset() addsimps add_ac@mult_ac) 1);
qed "zmult_congruent2";

(*Resolve th against the corresponding facts for zmult*)
val zmult_ize = RSLIST [equiv_intrel, zmult_congruent2];

Goalw [zmult_def]
   "Abs_Integ((intrel^^{(x1,y1)})) * Abs_Integ((intrel^^{(x2,y2)})) =   \
\   Abs_Integ(intrel ^^ {(x1*x2 + y1*y2, x1*y2 + y1*x2)})";
by (simp_tac (simpset() addsimps [zmult_ize UN_equiv_class2]) 1);
qed "zmult";

Goal "(- z) * w = - (z * (w::int))";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps ([zminus, zmult] @ add_ac)) 1);
qed "zmult_zminus";


Goal "(- z) * (- w) = (z * (w::int))";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps ([zminus, zmult] @ add_ac)) 1);
qed "zmult_zminus_zminus";

Goal "(z::int) * w = w * z";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps ([zmult] @ add_ac @ mult_ac)) 1);
qed "zmult_commute";

Goal "((z1::int) * z2) * z3 = z1 * (z2 * z3)";
by (res_inst_tac [("z","z1")] eq_Abs_Integ 1);
by (res_inst_tac [("z","z2")] eq_Abs_Integ 1);
by (res_inst_tac [("z","z3")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps ([add_mult_distrib2,zmult] @ 
                                     add_ac @ mult_ac)) 1);
qed "zmult_assoc";

(*For AC rewriting*)
Goal "(z1::int)*(z2*z3) = z2*(z1*z3)";
by (rtac (zmult_commute RS trans) 1);
by (rtac (zmult_assoc RS trans) 1);
by (rtac (zmult_commute RS arg_cong) 1);
qed "zmult_left_commute";

(*Integer multiplication is an AC operator*)
val zmult_ac = [zmult_assoc, zmult_commute, zmult_left_commute];

Goal "((z1::int) + z2) * w = (z1 * w) + (z2 * w)";
by (res_inst_tac [("z","z1")] eq_Abs_Integ 1);
by (res_inst_tac [("z","z2")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (asm_simp_tac 
    (simpset() addsimps ([add_mult_distrib2, zadd, zmult] @ 
			 add_ac @ mult_ac)) 1);
qed "zadd_zmult_distrib";

val zmult_commute'= read_instantiate [("z","w")] zmult_commute;

Goal "w * (- z) = - (w * (z::int))";
by (simp_tac (simpset() addsimps [zmult_commute', zmult_zminus]) 1);
qed "zmult_zminus_right";

Goal "(w::int) * (z1 + z2) = (w * z1) + (w * z2)";
by (simp_tac (simpset() addsimps [zmult_commute',zadd_zmult_distrib]) 1);
qed "zadd_zmult_distrib2";

Goalw [znat_def] "$# 0 * z = $# 0";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zmult]) 1);
qed "zmult_nat0";

Goalw [znat_def] "$# 1 * z = z";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (asm_simp_tac (simpset() addsimps [zmult]) 1);
qed "zmult_nat1";

Goal "z * $# 0 = $# 0";
by (rtac ([zmult_commute, zmult_nat0] MRS trans) 1);
qed "zmult_nat0_right";

Goal "z * $# 1 = z";
by (rtac ([zmult_commute, zmult_nat1] MRS trans) 1);
qed "zmult_nat1_right";

Addsimps [zmult_nat0, zmult_nat0_right, zmult_nat1, zmult_nat1_right];


Goal "(- z = w) = (z = - (w::int))";
by Safe_tac;
by (rtac (zminus_zminus RS sym) 1);
by (rtac zminus_zminus 1);
qed "zminus_exchange";


(* Theorems about less and less_equal *)

(*This lemma allows direct proofs of other <-properties*)
Goalw [zless_def, znegative_def, zdiff_def, znat_def] 
    "(w < z) = (EX n. z = w + $#(Suc n))";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by (Clarify_tac 1);
by (asm_full_simp_tac (simpset() addsimps [zadd, zminus]) 1);
by (safe_tac (claset() addSDs [less_eq_Suc_add]));
by (res_inst_tac [("x","k")] exI 1);
by (ALLGOALS (asm_full_simp_tac (simpset() addsimps add_ac)));
qed "zless_iff_Suc_zadd";

Goal "z < z + $# (Suc n)";
by (auto_tac (claset(),
	      simpset() addsimps [zless_iff_Suc_zadd, zadd_assoc, 
				  add_znat]));
qed "zless_zadd_Suc";

Goal "[| z1<z2; z2<z3 |] ==> z1 < (z3::int)";
by (auto_tac (claset(),
	      simpset() addsimps [zless_iff_Suc_zadd, zadd_assoc, 
				  add_znat]));
qed "zless_trans";

Goal "!!w::int. z<w ==> ~w<z";
by (safe_tac (claset() addSDs [zless_iff_Suc_zadd RS iffD1]));
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by Safe_tac;
by (asm_full_simp_tac (simpset() addsimps ([znat_def, zadd])) 1);
qed "zless_not_sym";

(* [| n<m;  ~P ==> m<n |] ==> P *)
bind_thm ("zless_asym", (zless_not_sym RS swap));

Goal "!!z::int. ~ z<z";
by (resolve_tac [zless_asym RS notI] 1);
by (REPEAT (assume_tac 1));
qed "zless_not_refl";

(* z<z ==> R *)
bind_thm ("zless_irrefl", (zless_not_refl RS notE));
AddSEs [zless_irrefl];

Goal "z<w ==> w ~= (z::int)";
by (Blast_tac 1);
qed "zless_not_refl2";

(* s < t ==> s ~= t *)
bind_thm ("zless_not_refl3", zless_not_refl2 RS not_sym);


(*"Less than" is a linear ordering*)
Goalw [zless_def, znegative_def, zdiff_def] 
    "z<w | z=w | w<(z::int)";
by (res_inst_tac [("z","z")] eq_Abs_Integ 1);
by (res_inst_tac [("z","w")] eq_Abs_Integ 1);
by Safe_tac;
by (asm_full_simp_tac
    (simpset() addsimps [zadd, zminus, Image_iff, Bex_def]) 1);
by (res_inst_tac [("m1", "x+ya"), ("n1", "xa+y")] (less_linear RS disjE) 1);
by (auto_tac (claset(), simpset() addsimps add_ac));
qed "zless_linear";

Goal "!!w::int. (w ~= z) = (w<z | z<w)";
by (cut_facts_tac [zless_linear] 1);
by (Blast_tac 1);
qed "int_neq_iff";

(*** eliminates ~= in premises ***)
bind_thm("int_neqE", int_neq_iff RS iffD1 RS disjE);

Goal "($# m = $# n) = (m = n)"; 
by (fast_tac (claset() addSEs [inj_znat RS injD]) 1); 
qed "znat_znat_eq"; 
AddIffs [znat_znat_eq]; 

Goal "($#m < $#n) = (m<n)";
by (simp_tac (simpset() addsimps [less_iff_Suc_add, zless_iff_Suc_zadd, 
				  add_znat]) 1);
qed "zless_eq_less";
Addsimps [zless_eq_less];


(*** Properties of <= ***)

Goalw [zle_def, le_def] "($#m <= $#n) = (m<=n)";
by (Simp_tac 1);
qed "zle_eq_le";
Addsimps [zle_eq_le];

Goalw [zle_def] "~(w<z) ==> z<=(w::int)";
by (assume_tac 1);
qed "zleI";

Goalw [zle_def] "z<=w ==> ~(w<(z::int))";
by (assume_tac 1);
qed "zleD";

(*  [| z <= w;  ~ P ==> w < z |] ==> P  *)
bind_thm ("zleE", zleD RS swap);

Goalw [zle_def] "(~w<=z) = (z<(w::int))";
by (Simp_tac 1);
qed "not_zle_iff_zless";

Goalw [zle_def] "~ z <= w ==> w<(z::int)";
by (Fast_tac 1);
qed "not_zleE";

Goalw [zle_def] "z <= w ==> z < w | z=(w::int)";
by (cut_facts_tac [zless_linear] 1);
by (blast_tac (claset() addEs [zless_asym]) 1);
qed "zle_imp_zless_or_eq";

Goalw [zle_def] "z<w | z=w ==> z <= (w::int)";
by (cut_facts_tac [zless_linear] 1);
by (blast_tac (claset() addEs [zless_asym]) 1);
qed "zless_or_eq_imp_zle";

Goal "(x <= (y::int)) = (x < y | x=y)";
by (REPEAT(ares_tac [iffI, zless_or_eq_imp_zle, zle_imp_zless_or_eq] 1));
qed "zle_eq_zless_or_eq";

Goal "w <= (w::int)";
by (simp_tac (simpset() addsimps [zle_eq_zless_or_eq]) 1);
qed "zle_refl";

Goalw [zle_def] "z < w ==> z <= (w::int)";
by (blast_tac (claset() addEs [zless_asym]) 1);
qed "zless_imp_zle";

Addsimps [zle_refl, zless_imp_zle];

(* Axiom 'linorder_linear' of class 'linorder': *)
Goal "(z::int) <= w | w <= z";
by (simp_tac (simpset() addsimps [zle_eq_zless_or_eq]) 1);
by (cut_facts_tac [zless_linear] 1);
by (Blast_tac 1);
qed "zle_linear";

Goal "[| i <= j; j < k |] ==> i < (k::int)";
by (dtac zle_imp_zless_or_eq 1);
by (blast_tac (claset() addIs [zless_trans]) 1);
qed "zle_zless_trans";

Goal "[| i < j; j <= k |] ==> i < (k::int)";
by (dtac zle_imp_zless_or_eq 1);
by (blast_tac (claset() addIs [zless_trans]) 1);
qed "zless_zle_trans";

Goal "[| i <= j; j <= k |] ==> i <= (k::int)";
by (EVERY1 [dtac zle_imp_zless_or_eq, dtac zle_imp_zless_or_eq,
            rtac zless_or_eq_imp_zle, 
	    blast_tac (claset() addIs [zless_trans])]);
qed "zle_trans";

Goal "[| z <= w; w <= z |] ==> z = (w::int)";
by (EVERY1 [dtac zle_imp_zless_or_eq, dtac zle_imp_zless_or_eq,
            blast_tac (claset() addEs [zless_asym])]);
qed "zle_anti_sym";

(* Axiom 'order_less_le' of class 'order': *)
Goal "(w::int) < z = (w <= z & w ~= z)";
by (simp_tac (simpset() addsimps [zle_def, int_neq_iff]) 1);
by (blast_tac (claset() addSEs [zless_asym]) 1);
qed "int_less_le";

(* [| w <= z; w ~= z |] ==> w < z *)
bind_thm ("zle_neq_implies_zless", [int_less_le, conjI] MRS iffD2);



(*** Subtraction laws ***)

Goal "x + (y - z) = (x + y) - (z::int)";
by (simp_tac (simpset() addsimps (zdiff_def::zadd_ac)) 1);
qed "zadd_zdiff_eq";

Goal "(x - y) + z = (x + z) - (y::int)";
by (simp_tac (simpset() addsimps (zdiff_def::zadd_ac)) 1);
qed "zdiff_zadd_eq";

Goal "(x - y) - z = x - (y + (z::int))";
by (simp_tac (simpset() addsimps (zdiff_def::zadd_ac)) 1);
qed "zdiff_zdiff_eq";

Goal "x - (y - z) = (x + z) - (y::int)";
by (simp_tac (simpset() addsimps (zdiff_def::zadd_ac)) 1);
qed "zdiff_zdiff_eq2";

Goalw [zless_def, zdiff_def] "(x-y < z) = (x < z + (y::int))";
by (simp_tac (simpset() addsimps zadd_ac) 1);
qed "zdiff_zless_eq";

Goalw [zless_def, zdiff_def] "(x < z-y) = (x + (y::int) < z)";
by (simp_tac (simpset() addsimps zadd_ac) 1);
qed "zless_zdiff_eq";

Goalw [zle_def] "(x-y <= z) = (x <= z + (y::int))";
by (simp_tac (simpset() addsimps [zless_zdiff_eq]) 1);
qed "zdiff_zle_eq";

Goalw [zle_def] "(x <= z-y) = (x + (y::int) <= z)";
by (simp_tac (simpset() addsimps [zdiff_zless_eq]) 1);
qed "zle_zdiff_eq";

Goalw [zdiff_def] "(x-y = z) = (x = z + (y::int))";
by (auto_tac (claset(), simpset() addsimps [zadd_assoc]));
qed "zdiff_eq_eq";

Goalw [zdiff_def] "(x = z-y) = (x + (y::int) = z)";
by (auto_tac (claset(), simpset() addsimps [zadd_assoc]));
qed "eq_zdiff_eq";

(*This list of rewrites simplifies (in)equalities by bringing subtractions
  to the top and then moving negative terms to the other side.  
  Use with zadd_ac*)
val zcompare_rls = 
    [symmetric zdiff_def,
     zadd_zdiff_eq, zdiff_zadd_eq, zdiff_zdiff_eq, zdiff_zdiff_eq2, 
     zdiff_zless_eq, zless_zdiff_eq, zdiff_zle_eq, zle_zdiff_eq, 
     zdiff_eq_eq, eq_zdiff_eq];


(** Cancellation laws **)

Goal "!!w::int. (z + w' = z + w) = (w' = w)";
by Safe_tac;
by (dres_inst_tac [("f", "%x. x + -z")] arg_cong 1);
by (asm_full_simp_tac (simpset() addsimps zadd_ac) 1);
qed "zadd_left_cancel";

Addsimps [zadd_left_cancel];

Goal "!!z::int. (w' + z = w + z) = (w' = w)";
by (asm_full_simp_tac (simpset() addsimps zadd_ac) 1);
qed "zadd_right_cancel";

Addsimps [zadd_right_cancel];


Goal "(w < z + $# 1) = (w<z | w=z)";
by (auto_tac (claset(),
	      simpset() addsimps [zless_iff_Suc_zadd, zadd_assoc, 
				  add_znat]));
by (cut_inst_tac [("m","n")] znat_Suc 1);
by (exhaust_tac "n" 1);
auto();
by (full_simp_tac (simpset() addsimps zadd_ac) 1);
by (asm_full_simp_tac (simpset() addsimps [zadd_assoc RS sym]) 1);
qed "zless_add_nat1_eq";


Goal "(w + $# 1 <= z) = (w<z)";
by (simp_tac (simpset() addsimps [zle_def, zless_add_nat1_eq]) 1);
by (auto_tac (claset() addIs [zle_anti_sym] addEs [zless_asym],
	      simpset() addsimps [symmetric zle_def]));
qed "add_nat1_zle_eq";