src/HOL/Integ/int_arith1.ML
author paulson
Mon Oct 22 11:54:22 2001 +0200 (2001-10-22)
changeset 11868 56db9f3a6b3e
parent 11713 883d559b0b8c
child 12018 ec054019c910
permissions -rw-r--r--
Numerals now work for the integers: the binary numerals for 0 and 1 rewrite
to their abstract counterparts, while other binary numerals work correctly.
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(*  Title:      HOL/Integ/int_arith1.ML
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    ID:         $Id$
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    Authors:    Larry Paulson and Tobias Nipkow
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Simprocs and decision procedure for linear arithmetic.
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*)
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Addsimps [int_numeral_0_eq_0, int_numeral_1_eq_1];
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(*** Simprocs for numeric literals ***)
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(** Combining of literal coefficients in sums of products **)
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Goal "(x < y) = (x-y < (0::int))";
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by (simp_tac (simpset() addsimps zcompare_rls) 1);
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qed "zless_iff_zdiff_zless_0";
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Goal "(x = y) = (x-y = (0::int))";
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by (simp_tac (simpset() addsimps zcompare_rls) 1);
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qed "eq_iff_zdiff_eq_0";
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Goal "(x <= y) = (x-y <= (0::int))";
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by (simp_tac (simpset() addsimps zcompare_rls) 1);
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qed "zle_iff_zdiff_zle_0";
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(** For combine_numerals **)
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Goal "i*u + (j*u + k) = (i+j)*u + (k::int)";
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by (asm_simp_tac (simpset() addsimps [zadd_zmult_distrib]) 1);
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qed "left_zadd_zmult_distrib";
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(** For cancel_numerals **)
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val rel_iff_rel_0_rls = map (inst "y" "?u+?v")
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                          [zless_iff_zdiff_zless_0, eq_iff_zdiff_eq_0, 
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			   zle_iff_zdiff_zle_0] @
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		        map (inst "y" "n")
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                          [zless_iff_zdiff_zless_0, eq_iff_zdiff_eq_0, 
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			   zle_iff_zdiff_zle_0];
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Goal "!!i::int. (i*u + m = j*u + n) = ((i-j)*u + m = n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
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		                     zadd_ac@rel_iff_rel_0_rls) 1);
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qed "eq_add_iff1";
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Goal "!!i::int. (i*u + m = j*u + n) = (m = (j-i)*u + n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
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                                     zadd_ac@rel_iff_rel_0_rls) 1);
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qed "eq_add_iff2";
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Goal "!!i::int. (i*u + m < j*u + n) = ((i-j)*u + m < n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
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                                     zadd_ac@rel_iff_rel_0_rls) 1);
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qed "less_add_iff1";
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Goal "!!i::int. (i*u + m < j*u + n) = (m < (j-i)*u + n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
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                                     zadd_ac@rel_iff_rel_0_rls) 1);
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qed "less_add_iff2";
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Goal "!!i::int. (i*u + m <= j*u + n) = ((i-j)*u + m <= n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
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                                     zadd_ac@rel_iff_rel_0_rls) 1);
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qed "le_add_iff1";
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Goal "!!i::int. (i*u + m <= j*u + n) = (m <= (j-i)*u + n)";
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by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]
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                                     @zadd_ac@rel_iff_rel_0_rls) 1);
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qed "le_add_iff2";
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(*To tidy up the result of a simproc.  Only the RHS will be simplified.*)
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Goal "u = u' ==> (t==u) == (t==u')";
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by Auto_tac;
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qed "eq_cong2";
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structure Int_Numeral_Simprocs =
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struct
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(*Maps 0 to Numeral0 and 1 to Numeral1 so that arithmetic in simprocs
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  isn't complicated by the abstract 0 and 1.*)
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val numeral_syms = [int_numeral_0_eq_0 RS sym, int_numeral_1_eq_1 RS sym];
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val numeral_sym_ss = HOL_ss addsimps numeral_syms;
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fun rename_numerals th = 
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    simplify numeral_sym_ss (Thm.transfer (the_context ()) th);
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(*Utilities*)
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fun mk_numeral n = HOLogic.number_of_const HOLogic.intT $ HOLogic.mk_bin n;
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(*Decodes a binary INTEGER*)
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fun dest_numeral (Const("0", _)) = 0
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  | dest_numeral (Const("1", _)) = 1
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  | dest_numeral (Const("Numeral.number_of", _) $ w) = 
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     (HOLogic.dest_binum w
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      handle TERM _ => raise TERM("Int_Numeral_Simprocs.dest_numeral:1", [w]))
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  | dest_numeral t = raise TERM("Int_Numeral_Simprocs.dest_numeral:2", [t]);
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fun find_first_numeral past (t::terms) =
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	((dest_numeral t, rev past @ terms)
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	 handle TERM _ => find_first_numeral (t::past) terms)
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  | find_first_numeral past [] = raise TERM("find_first_numeral", []);
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val zero = mk_numeral 0;
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val mk_plus = HOLogic.mk_binop "op +";
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val uminus_const = Const ("uminus", HOLogic.intT --> HOLogic.intT);
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(*Thus mk_sum[t] yields t+0; longer sums don't have a trailing zero*)
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fun mk_sum []        = zero
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  | mk_sum [t,u]     = mk_plus (t, u)
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  | mk_sum (t :: ts) = mk_plus (t, mk_sum ts);
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(*this version ALWAYS includes a trailing zero*)
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fun long_mk_sum []        = zero
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  | long_mk_sum (t :: ts) = mk_plus (t, mk_sum ts);
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val dest_plus = HOLogic.dest_bin "op +" HOLogic.intT;
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(*decompose additions AND subtractions as a sum*)
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fun dest_summing (pos, Const ("op +", _) $ t $ u, ts) =
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        dest_summing (pos, t, dest_summing (pos, u, ts))
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  | dest_summing (pos, Const ("op -", _) $ t $ u, ts) =
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        dest_summing (pos, t, dest_summing (not pos, u, ts))
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  | dest_summing (pos, t, ts) =
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	if pos then t::ts else uminus_const$t :: ts;
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fun dest_sum t = dest_summing (true, t, []);
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val mk_diff = HOLogic.mk_binop "op -";
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val dest_diff = HOLogic.dest_bin "op -" HOLogic.intT;
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val one = mk_numeral 1;
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val mk_times = HOLogic.mk_binop "op *";
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fun mk_prod [] = one
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  | mk_prod [t] = t
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  | mk_prod (t :: ts) = if t = one then mk_prod ts
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                        else mk_times (t, mk_prod ts);
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val dest_times = HOLogic.dest_bin "op *" HOLogic.intT;
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fun dest_prod t =
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      let val (t,u) = dest_times t 
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      in  dest_prod t @ dest_prod u  end
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      handle TERM _ => [t];
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(*DON'T do the obvious simplifications; that would create special cases*) 
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fun mk_coeff (k, ts) = mk_times (mk_numeral k, ts);
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(*Express t as a product of (possibly) a numeral with other sorted terms*)
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fun dest_coeff sign (Const ("uminus", _) $ t) = dest_coeff (~sign) t
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  | dest_coeff sign t =
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    let val ts = sort Term.term_ord (dest_prod t)
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	val (n, ts') = find_first_numeral [] ts
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                          handle TERM _ => (1, ts)
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    in (sign*n, mk_prod ts') end;
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(*Find first coefficient-term THAT MATCHES u*)
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fun find_first_coeff past u [] = raise TERM("find_first_coeff", []) 
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  | find_first_coeff past u (t::terms) =
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	let val (n,u') = dest_coeff 1 t
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	in  if u aconv u' then (n, rev past @ terms)
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			  else find_first_coeff (t::past) u terms
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	end
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	handle TERM _ => find_first_coeff (t::past) u terms;
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(*Simplify Numeral0+n, n+Numeral0, Numeral1*n, n*Numeral1*)
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val add_0s =  map rename_numerals [zadd_0, zadd_0_right];
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val mult_1s = map rename_numerals [zmult_1, zmult_1_right] @
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              [zmult_minus1, zmult_minus1_right];
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(*To perform binary arithmetic.  The "left" rewriting handles patterns
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  created by the simprocs, such as 3 * (5 * x). *)
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val bin_simps = [int_numeral_0_eq_0 RS sym, int_numeral_1_eq_1 RS sym,
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                 add_number_of_left, mult_number_of_left] @ 
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                bin_arith_simps @ bin_rel_simps;
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(*To evaluate binary negations of coefficients*)
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val zminus_simps = NCons_simps @
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                   [zminus_1_eq_m1, number_of_minus RS sym, 
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		    bin_minus_1, bin_minus_0, bin_minus_Pls, bin_minus_Min,
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		    bin_pred_1, bin_pred_0, bin_pred_Pls, bin_pred_Min];
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(*To let us treat subtraction as addition*)
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val diff_simps = [zdiff_def, zminus_zadd_distrib, zminus_zminus];
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(*push the unary minus down: - x * y = x * - y *)
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val int_minus_mult_eq_1_to_2 = 
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    [zmult_zminus, zmult_zminus_right RS sym] MRS trans |> standard;
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(*to extract again any uncancelled minuses*)
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val int_minus_from_mult_simps = 
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    [zminus_zminus, zmult_zminus, zmult_zminus_right];
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(*combine unary minus with numeric literals, however nested within a product*)
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val int_mult_minus_simps =
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    [zmult_assoc, zmult_zminus RS sym, int_minus_mult_eq_1_to_2];
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(*Apply the given rewrite (if present) just once*)
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fun trans_tac None      = all_tac
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  | trans_tac (Some th) = ALLGOALS (rtac (th RS trans));
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fun simplify_meta_eq rules =
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    mk_meta_eq o
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    simplify (HOL_basic_ss addeqcongs[eq_cong2] addsimps rules)
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structure CancelNumeralsCommon =
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  struct
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  val mk_sum    	= mk_sum
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  val dest_sum		= dest_sum
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  val mk_coeff		= mk_coeff
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  val dest_coeff	= dest_coeff 1
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  val find_first_coeff	= find_first_coeff []
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  val trans_tac         = trans_tac
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  val norm_tac = 
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     ALLGOALS (simp_tac (HOL_ss addsimps numeral_syms@add_0s@mult_1s@
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                                         diff_simps@zminus_simps@zadd_ac))
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     THEN ALLGOALS (simp_tac (HOL_ss addsimps bin_simps@int_mult_minus_simps))
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     THEN ALLGOALS (simp_tac (HOL_ss addsimps int_minus_from_mult_simps@
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                                              zadd_ac@zmult_ac))
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  val numeral_simp_tac	= ALLGOALS (simp_tac (HOL_ss addsimps add_0s@bin_simps))
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  val simplify_meta_eq  = simplify_meta_eq (add_0s@mult_1s)
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  end;
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structure EqCancelNumerals = CancelNumeralsFun
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 (open CancelNumeralsCommon
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  val prove_conv = Bin_Simprocs.prove_conv "inteq_cancel_numerals"
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  val mk_bal   = HOLogic.mk_eq
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  val dest_bal = HOLogic.dest_bin "op =" HOLogic.intT
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  val bal_add1 = eq_add_iff1 RS trans
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  val bal_add2 = eq_add_iff2 RS trans
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);
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structure LessCancelNumerals = CancelNumeralsFun
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 (open CancelNumeralsCommon
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  val prove_conv = Bin_Simprocs.prove_conv "intless_cancel_numerals"
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  val mk_bal   = HOLogic.mk_binrel "op <"
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  val dest_bal = HOLogic.dest_bin "op <" HOLogic.intT
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  val bal_add1 = less_add_iff1 RS trans
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  val bal_add2 = less_add_iff2 RS trans
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);
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structure LeCancelNumerals = CancelNumeralsFun
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 (open CancelNumeralsCommon
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  val prove_conv = Bin_Simprocs.prove_conv "intle_cancel_numerals"
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  val mk_bal   = HOLogic.mk_binrel "op <="
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  val dest_bal = HOLogic.dest_bin "op <=" HOLogic.intT
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  val bal_add1 = le_add_iff1 RS trans
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  val bal_add2 = le_add_iff2 RS trans
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);
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val cancel_numerals = 
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  map Bin_Simprocs.prep_simproc
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   [("inteq_cancel_numerals",
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     Bin_Simprocs.prep_pats
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               ["(l::int) + m = n", "(l::int) = m + n", 
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		"(l::int) - m = n", "(l::int) = m - n", 
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		"(l::int) * m = n", "(l::int) = m * n"], 
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     EqCancelNumerals.proc),
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    ("intless_cancel_numerals", 
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     Bin_Simprocs.prep_pats
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               ["(l::int) + m < n", "(l::int) < m + n", 
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		"(l::int) - m < n", "(l::int) < m - n", 
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		"(l::int) * m < n", "(l::int) < m * n"], 
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     LessCancelNumerals.proc),
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    ("intle_cancel_numerals", 
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     Bin_Simprocs.prep_pats
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               ["(l::int) + m <= n", "(l::int) <= m + n", 
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		"(l::int) - m <= n", "(l::int) <= m - n", 
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		"(l::int) * m <= n", "(l::int) <= m * n"], 
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     LeCancelNumerals.proc)];
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structure CombineNumeralsData =
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  struct
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  val add		= op + : int*int -> int 
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  val mk_sum    	= long_mk_sum    (*to work for e.g. 2*x + 3*x *)
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  val dest_sum		= dest_sum
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  val mk_coeff		= mk_coeff
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  val dest_coeff	= dest_coeff 1
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  val left_distrib	= left_zadd_zmult_distrib RS trans
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  val prove_conv        = Bin_Simprocs.prove_conv_nohyps "int_combine_numerals"
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  val trans_tac          = trans_tac
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  val norm_tac = 
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     ALLGOALS (simp_tac (HOL_ss addsimps numeral_syms@add_0s@mult_1s@
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                                         diff_simps@zminus_simps@zadd_ac))
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     THEN ALLGOALS (simp_tac (HOL_ss addsimps bin_simps@int_mult_minus_simps))
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     THEN ALLGOALS (simp_tac (HOL_ss addsimps int_minus_from_mult_simps@
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                                              zadd_ac@zmult_ac))
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  val numeral_simp_tac	= ALLGOALS 
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                    (simp_tac (HOL_ss addsimps add_0s@bin_simps))
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  val simplify_meta_eq  = simplify_meta_eq (add_0s@mult_1s)
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  end;
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structure CombineNumerals = CombineNumeralsFun(CombineNumeralsData);
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val combine_numerals = Bin_Simprocs.prep_simproc
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                 ("int_combine_numerals",
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		  Bin_Simprocs.prep_pats ["(i::int) + j", "(i::int) - j"],
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		  CombineNumerals.proc);
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end;
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Addsimprocs Int_Numeral_Simprocs.cancel_numerals;
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Addsimprocs [Int_Numeral_Simprocs.combine_numerals];
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(*The Abel_Cancel simprocs are now obsolete*)
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Delsimprocs [Int_Cancel.sum_conv, Int_Cancel.rel_conv];
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(*examples:
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print_depth 22;
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set timing;
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set trace_simp;
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fun test s = (Goal s, by (Simp_tac 1)); 
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test "l + 2 + 2 + 2 + (l + 2) + (oo + 2) = (uu::int)";
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test "2*u = (u::int)";
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test "(i + j + 12 + (k::int)) - 15 = y";
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test "(i + j + 12 + (k::int)) - 5 = y";
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test "y - b < (b::int)";
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test "y - (3*b + c) < (b::int) - 2*c";
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test "(2*x - (u*v) + y) - v*3*u = (w::int)";
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test "(2*x*u*v + (u*v)*4 + y) - v*u*4 = (w::int)";
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test "(2*x*u*v + (u*v)*4 + y) - v*u = (w::int)";
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test "u*v - (x*u*v + (u*v)*4 + y) = (w::int)";
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test "(i + j + 12 + (k::int)) = u + 15 + y";
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test "(i + j*2 + 12 + (k::int)) = j + 5 + y";
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test "2*y + 3*z + 6*w + 2*y + 3*z + 2*u = 2*y' + 3*z' + 6*w' + 2*y' + 3*z' + u + (vv::int)";
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test "a + -(b+c) + b = (d::int)";
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test "a + -(b+c) - b = (d::int)";
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(*negative numerals*)
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test "(i + j + -2 + (k::int)) - (u + 5 + y) = zz";
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test "(i + j + -3 + (k::int)) < u + 5 + y";
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test "(i + j + 3 + (k::int)) < u + -6 + y";
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test "(i + j + -12 + (k::int)) - 15 = y";
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test "(i + j + 12 + (k::int)) - -15 = y";
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test "(i + j + -12 + (k::int)) - -15 = y";
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*)
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(** Constant folding for integer plus and times **)
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(*We do not need
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    structure Nat_Plus_Assoc = Assoc_Fold (Nat_Plus_Assoc_Data);
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    structure Int_Plus_Assoc = Assoc_Fold (Int_Plus_Assoc_Data);
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  because combine_numerals does the same thing*)
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structure Int_Times_Assoc_Data : ASSOC_FOLD_DATA =
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struct
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  val ss		= HOL_ss
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  val eq_reflection	= eq_reflection
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  val sg_ref = Sign.self_ref (Theory.sign_of (the_context ()))
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  val T	     = HOLogic.intT
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  val plus   = Const ("op *", [HOLogic.intT,HOLogic.intT] ---> HOLogic.intT);
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  val add_ac = zmult_ac
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   369
end;
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structure Int_Times_Assoc = Assoc_Fold (Int_Times_Assoc_Data);
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Addsimprocs [Int_Times_Assoc.conv];
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(** The same for the naturals **)
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structure Nat_Times_Assoc_Data : ASSOC_FOLD_DATA =
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struct
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  val ss		= HOL_ss
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  val eq_reflection	= eq_reflection
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  val sg_ref = Sign.self_ref (Theory.sign_of (the_context ()))
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  val T	     = HOLogic.natT
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  val plus   = Const ("op *", [HOLogic.natT,HOLogic.natT] ---> HOLogic.natT);
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  val add_ac = mult_ac
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   386
end;
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   387
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   388
structure Nat_Times_Assoc = Assoc_Fold (Nat_Times_Assoc_Data);
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   389
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   390
Addsimprocs [Nat_Times_Assoc.conv];
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   391
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   392
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   393
(*** decision procedure for linear arithmetic ***)
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   394
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   395
(*---------------------------------------------------------------------------*)
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   396
(* Linear arithmetic                                                         *)
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   397
(*---------------------------------------------------------------------------*)
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   398
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   399
(*
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Instantiation of the generic linear arithmetic package for int.
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   401
*)
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   402
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   403
(* Update parameters of arithmetic prover *)
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   404
local
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   405
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   406
(* reduce contradictory <= to False *)
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   407
val add_rules = 
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   408
    simp_thms @ bin_arith_simps @ bin_rel_simps @ 
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   409
    [int_numeral_0_eq_0, int_numeral_1_eq_1,
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   410
     zadd_0, zadd_0_right, zdiff_def,
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   411
     zadd_zminus_inverse, zadd_zminus_inverse2, 
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   412
     zmult_0, zmult_0_right, 
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   413
     zmult_1, zmult_1_right, 
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   414
     zmult_minus1, zmult_minus1_right,
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   415
     zminus_zadd_distrib, zminus_zminus, zmult_assoc,
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   416
     int_0, int_1, zadd_int RS sym, int_Suc];
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   417
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   418
val simprocs = [Int_Times_Assoc.conv, Int_Numeral_Simprocs.combine_numerals]@
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   419
               Int_Numeral_Simprocs.cancel_numerals @ 
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   420
               Bin_Simprocs.eval_numerals;
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   421
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   422
val add_mono_thms_int =
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   423
  map (fn s => prove_goal (the_context ()) s
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   424
                 (fn prems => [cut_facts_tac prems 1,
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   425
                      asm_simp_tac (simpset() addsimps [zadd_zle_mono]) 1]))
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   426
    ["(i <= j) & (k <= l) ==> i + k <= j + (l::int)",
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   427
     "(i  = j) & (k <= l) ==> i + k <= j + (l::int)",
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   428
     "(i <= j) & (k  = l) ==> i + k <= j + (l::int)",
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   429
     "(i  = j) & (k  = l) ==> i + k  = j + (l::int)"
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   430
    ];
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   431
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   432
in
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   433
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   434
val int_arith_setup =
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   435
 [Fast_Arith.map_data (fn {add_mono_thms, mult_mono_thms, inj_thms, lessD, simpset} =>
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   436
   {add_mono_thms = add_mono_thms @ add_mono_thms_int,
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   437
    mult_mono_thms = mult_mono_thms,
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   438
    inj_thms = [zle_int RS iffD2,int_int_eq RS iffD2] @ inj_thms,
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   439
    lessD = lessD @ [add1_zle_eq RS iffD2],
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   440
    simpset = simpset addsimps add_rules
wenzelm@9436
   441
                      addsimprocs simprocs
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   442
                      addcongs [if_weak_cong]}),
nipkow@10834
   443
  arith_inj_const ("IntDef.int", HOLogic.natT --> HOLogic.intT),
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   444
  arith_discrete ("IntDef.int", true)];
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   445
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   446
end;
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   447
wenzelm@9436
   448
let
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   449
val int_arith_simproc_pats =
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   450
  map (fn s => Thm.read_cterm (Theory.sign_of (the_context())) (s, HOLogic.boolT))
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   451
      ["(m::int) < n","(m::int) <= n", "(m::int) = n"];
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   452
wenzelm@9436
   453
val fast_int_arith_simproc = mk_simproc
wenzelm@9436
   454
  "fast_int_arith" int_arith_simproc_pats Fast_Arith.lin_arith_prover;
wenzelm@9436
   455
in
wenzelm@9436
   456
Addsimprocs [fast_int_arith_simproc]
wenzelm@9436
   457
end;
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   458
wenzelm@9436
   459
(* Some test data
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   460
Goal "!!a::int. [| a <= b; c <= d; x+y<z |] ==> a+c <= b+d";
wenzelm@9436
   461
by (fast_arith_tac 1);
wenzelm@11704
   462
Goal "!!a::int. [| a < b; c < d |] ==> a-d+ 2 <= b+(-c)";
wenzelm@9436
   463
by (fast_arith_tac 1);
paulson@11868
   464
Goal "!!a::int. [| a < b; c < d |] ==> a+c+ 1 < b+d";
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   465
by (fast_arith_tac 1);
wenzelm@9436
   466
Goal "!!a::int. [| a <= b; b+b <= c |] ==> a+a <= c";
wenzelm@9436
   467
by (fast_arith_tac 1);
wenzelm@9436
   468
Goal "!!a::int. [| a+b <= i+j; a<=b; i<=j |] \
wenzelm@9436
   469
\     ==> a+a <= j+j";
wenzelm@9436
   470
by (fast_arith_tac 1);
wenzelm@9436
   471
Goal "!!a::int. [| a+b < i+j; a<b; i<j |] \
wenzelm@11704
   472
\     ==> a+a - - -1 < j+j - 3";
wenzelm@9436
   473
by (fast_arith_tac 1);
wenzelm@9436
   474
Goal "!!a::int. a+b+c <= i+j+k & a<=b & b<=c & i<=j & j<=k --> a+a+a <= k+k+k";
wenzelm@9436
   475
by (arith_tac 1);
wenzelm@9436
   476
Goal "!!a::int. [| a+b+c+d <= i+j+k+l; a<=b; b<=c; c<=d; i<=j; j<=k; k<=l |] \
wenzelm@9436
   477
\     ==> a <= l";
wenzelm@9436
   478
by (fast_arith_tac 1);
wenzelm@9436
   479
Goal "!!a::int. [| a+b+c+d <= i+j+k+l; a<=b; b<=c; c<=d; i<=j; j<=k; k<=l |] \
wenzelm@9436
   480
\     ==> a+a+a+a <= l+l+l+l";
wenzelm@9436
   481
by (fast_arith_tac 1);
wenzelm@9436
   482
Goal "!!a::int. [| a+b+c+d <= i+j+k+l; a<=b; b<=c; c<=d; i<=j; j<=k; k<=l |] \
wenzelm@9436
   483
\     ==> a+a+a+a+a <= l+l+l+l+i";
wenzelm@9436
   484
by (fast_arith_tac 1);
wenzelm@9436
   485
Goal "!!a::int. [| a+b+c+d <= i+j+k+l; a<=b; b<=c; c<=d; i<=j; j<=k; k<=l |] \
wenzelm@9436
   486
\     ==> a+a+a+a+a+a <= l+l+l+l+i+l";
wenzelm@9436
   487
by (fast_arith_tac 1);
wenzelm@9436
   488
Goal "!!a::int. [| a+b+c+d <= i+j+k+l; a<=b; b<=c; c<=d; i<=j; j<=k; k<=l |] \
wenzelm@11704
   489
\     ==> 6*a <= 5*l+i";
wenzelm@9436
   490
by (fast_arith_tac 1);
wenzelm@9436
   491
*)