src/ZF/int_arith.ML
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     1 (*  Title:      ZF/int_arith.ML
       
     2     ID:         $Id$
       
     3     Author:     Larry Paulson
       
     4     Copyright   2000  University of Cambridge
       
     5 
       
     6 Simprocs for linear arithmetic.
       
     7 *)
       
     8 
       
     9 
       
    10 (** To simplify inequalities involving integer negation and literals,
       
    11     such as -x = #3
       
    12 **)
       
    13 
       
    14 Addsimps [inst "y" "integ_of(?w)" zminus_equation,
       
    15           inst "x" "integ_of(?w)" equation_zminus];
       
    16 
       
    17 AddIffs [inst "y" "integ_of(?w)" zminus_zless,
       
    18          inst "x" "integ_of(?w)" zless_zminus];
       
    19 
       
    20 AddIffs [inst "y" "integ_of(?w)" zminus_zle,
       
    21          inst "x" "integ_of(?w)" zle_zminus];
       
    22 
       
    23 Addsimps [inst "s" "integ_of(?w)" (thm "Let_def")];
       
    24 
       
    25 (*** Simprocs for numeric literals ***)
       
    26 
       
    27 (** Combining of literal coefficients in sums of products **)
       
    28 
       
    29 Goal "(x $< y) <-> (x$-y $< #0)";
       
    30 by (simp_tac (simpset() addsimps zcompare_rls) 1);
       
    31 qed "zless_iff_zdiff_zless_0";
       
    32 
       
    33 Goal "[| x: int; y: int |] ==> (x = y) <-> (x$-y = #0)";
       
    34 by (asm_simp_tac (simpset() addsimps zcompare_rls) 1);
       
    35 qed "eq_iff_zdiff_eq_0";
       
    36 
       
    37 Goal "(x $<= y) <-> (x$-y $<= #0)";
       
    38 by (asm_simp_tac (simpset() addsimps zcompare_rls) 1);
       
    39 qed "zle_iff_zdiff_zle_0";
       
    40 
       
    41 
       
    42 (** For combine_numerals **)
       
    43 
       
    44 Goal "i$*u $+ (j$*u $+ k) = (i$+j)$*u $+ k";
       
    45 by (simp_tac (simpset() addsimps [zadd_zmult_distrib]@zadd_ac) 1);
       
    46 qed "left_zadd_zmult_distrib";
       
    47 
       
    48 
       
    49 (** For cancel_numerals **)
       
    50 
       
    51 val rel_iff_rel_0_rls = map (inst "y" "?u$+?v")
       
    52                           [zless_iff_zdiff_zless_0, eq_iff_zdiff_eq_0,
       
    53                            zle_iff_zdiff_zle_0] @
       
    54                         map (inst "y" "n")
       
    55                           [zless_iff_zdiff_zless_0, eq_iff_zdiff_eq_0,
       
    56                            zle_iff_zdiff_zle_0];
       
    57 
       
    58 Goal "(i$*u $+ m = j$*u $+ n) <-> ((i$-j)$*u $+ m = intify(n))";
       
    59 by (simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]) 1);
       
    60 by (simp_tac (simpset() addsimps zcompare_rls) 1);
       
    61 by (simp_tac (simpset() addsimps zadd_ac) 1);
       
    62 qed "eq_add_iff1";
       
    63 
       
    64 Goal "(i$*u $+ m = j$*u $+ n) <-> (intify(m) = (j$-i)$*u $+ n)";
       
    65 by (simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]) 1);
       
    66 by (simp_tac (simpset() addsimps zcompare_rls) 1);
       
    67 by (simp_tac (simpset() addsimps zadd_ac) 1);
       
    68 qed "eq_add_iff2";
       
    69 
       
    70 Goal "(i$*u $+ m $< j$*u $+ n) <-> ((i$-j)$*u $+ m $< n)";
       
    71 by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
       
    72                                      zadd_ac@rel_iff_rel_0_rls) 1);
       
    73 qed "less_add_iff1";
       
    74 
       
    75 Goal "(i$*u $+ m $< j$*u $+ n) <-> (m $< (j$-i)$*u $+ n)";
       
    76 by (asm_simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]@
       
    77                                      zadd_ac@rel_iff_rel_0_rls) 1);
       
    78 qed "less_add_iff2";
       
    79 
       
    80 Goal "(i$*u $+ m $<= j$*u $+ n) <-> ((i$-j)$*u $+ m $<= n)";
       
    81 by (simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]) 1);
       
    82 by (simp_tac (simpset() addsimps zcompare_rls) 1);
       
    83 by (simp_tac (simpset() addsimps zadd_ac) 1);
       
    84 qed "le_add_iff1";
       
    85 
       
    86 Goal "(i$*u $+ m $<= j$*u $+ n) <-> (m $<= (j$-i)$*u $+ n)";
       
    87 by (simp_tac (simpset() addsimps [zdiff_def, zadd_zmult_distrib]) 1);
       
    88 by (simp_tac (simpset() addsimps zcompare_rls) 1);
       
    89 by (simp_tac (simpset() addsimps zadd_ac) 1);
       
    90 qed "le_add_iff2";
       
    91 
       
    92 
       
    93 structure Int_Numeral_Simprocs =
       
    94 struct
       
    95 
       
    96 (*Utilities*)
       
    97 
       
    98 val integ_of_const = Const ("Bin.integ_of", iT --> iT);
       
    99 
       
   100 fun mk_numeral n = integ_of_const $ NumeralSyntax.mk_bin n;
       
   101 
       
   102 (*Decodes a binary INTEGER*)
       
   103 fun dest_numeral (Const("Bin.integ_of", _) $ w) =
       
   104      (NumeralSyntax.dest_bin w
       
   105       handle Match => raise TERM("Int_Numeral_Simprocs.dest_numeral:1", [w]))
       
   106   | dest_numeral t =  raise TERM("Int_Numeral_Simprocs.dest_numeral:2", [t]);
       
   107 
       
   108 fun find_first_numeral past (t::terms) =
       
   109         ((dest_numeral t, rev past @ terms)
       
   110          handle TERM _ => find_first_numeral (t::past) terms)
       
   111   | find_first_numeral past [] = raise TERM("find_first_numeral", []);
       
   112 
       
   113 val zero = mk_numeral 0;
       
   114 val mk_plus = FOLogic.mk_binop "Int.zadd";
       
   115 
       
   116 val iT = Ind_Syntax.iT;
       
   117 
       
   118 val zminus_const = Const ("Int.zminus", iT --> iT);
       
   119 
       
   120 (*Thus mk_sum[t] yields t+#0; longer sums don't have a trailing zero*)
       
   121 fun mk_sum []        = zero
       
   122   | mk_sum [t,u]     = mk_plus (t, u)
       
   123   | mk_sum (t :: ts) = mk_plus (t, mk_sum ts);
       
   124 
       
   125 (*this version ALWAYS includes a trailing zero*)
       
   126 fun long_mk_sum []        = zero
       
   127   | long_mk_sum (t :: ts) = mk_plus (t, mk_sum ts);
       
   128 
       
   129 val dest_plus = FOLogic.dest_bin "Int.zadd" iT;
       
   130 
       
   131 (*decompose additions AND subtractions as a sum*)
       
   132 fun dest_summing (pos, Const ("Int.zadd", _) $ t $ u, ts) =
       
   133         dest_summing (pos, t, dest_summing (pos, u, ts))
       
   134   | dest_summing (pos, Const ("Int.zdiff", _) $ t $ u, ts) =
       
   135         dest_summing (pos, t, dest_summing (not pos, u, ts))
       
   136   | dest_summing (pos, t, ts) =
       
   137         if pos then t::ts else zminus_const$t :: ts;
       
   138 
       
   139 fun dest_sum t = dest_summing (true, t, []);
       
   140 
       
   141 val mk_diff = FOLogic.mk_binop "Int.zdiff";
       
   142 val dest_diff = FOLogic.dest_bin "Int.zdiff" iT;
       
   143 
       
   144 val one = mk_numeral 1;
       
   145 val mk_times = FOLogic.mk_binop "Int.zmult";
       
   146 
       
   147 fun mk_prod [] = one
       
   148   | mk_prod [t] = t
       
   149   | mk_prod (t :: ts) = if t = one then mk_prod ts
       
   150                         else mk_times (t, mk_prod ts);
       
   151 
       
   152 val dest_times = FOLogic.dest_bin "Int.zmult" iT;
       
   153 
       
   154 fun dest_prod t =
       
   155       let val (t,u) = dest_times t
       
   156       in  dest_prod t @ dest_prod u  end
       
   157       handle TERM _ => [t];
       
   158 
       
   159 (*DON'T do the obvious simplifications; that would create special cases*)
       
   160 fun mk_coeff (k, t) = mk_times (mk_numeral k, t);
       
   161 
       
   162 (*Express t as a product of (possibly) a numeral with other sorted terms*)
       
   163 fun dest_coeff sign (Const ("Int.zminus", _) $ t) = dest_coeff (~sign) t
       
   164   | dest_coeff sign t =
       
   165     let val ts = sort Term.term_ord (dest_prod t)
       
   166         val (n, ts') = find_first_numeral [] ts
       
   167                           handle TERM _ => (1, ts)
       
   168     in (sign*n, mk_prod ts') end;
       
   169 
       
   170 (*Find first coefficient-term THAT MATCHES u*)
       
   171 fun find_first_coeff past u [] = raise TERM("find_first_coeff", [])
       
   172   | find_first_coeff past u (t::terms) =
       
   173         let val (n,u') = dest_coeff 1 t
       
   174         in  if u aconv u' then (n, rev past @ terms)
       
   175                           else find_first_coeff (t::past) u terms
       
   176         end
       
   177         handle TERM _ => find_first_coeff (t::past) u terms;
       
   178 
       
   179 
       
   180 (*Simplify #1*n and n*#1 to n*)
       
   181 val add_0s = [zadd_0_intify, zadd_0_right_intify];
       
   182 
       
   183 val mult_1s = [zmult_1_intify, zmult_1_right_intify,
       
   184                zmult_minus1, zmult_minus1_right];
       
   185 
       
   186 val tc_rules = [integ_of_type, intify_in_int,
       
   187                 int_of_type, zadd_type, zdiff_type, zmult_type] @ 
       
   188                thms "bin.intros";
       
   189 val intifys = [intify_ident, zadd_intify1, zadd_intify2,
       
   190                zdiff_intify1, zdiff_intify2, zmult_intify1, zmult_intify2,
       
   191                zless_intify1, zless_intify2, zle_intify1, zle_intify2];
       
   192 
       
   193 (*To perform binary arithmetic*)
       
   194 val bin_simps = [add_integ_of_left] @ bin_arith_simps @ bin_rel_simps;
       
   195 
       
   196 (*To evaluate binary negations of coefficients*)
       
   197 val zminus_simps = NCons_simps @
       
   198                    [integ_of_minus RS sym,
       
   199                     bin_minus_1, bin_minus_0, bin_minus_Pls, bin_minus_Min,
       
   200                     bin_pred_1, bin_pred_0, bin_pred_Pls, bin_pred_Min];
       
   201 
       
   202 (*To let us treat subtraction as addition*)
       
   203 val diff_simps = [zdiff_def, zminus_zadd_distrib, zminus_zminus];
       
   204 
       
   205 (*push the unary minus down: - x * y = x * - y *)
       
   206 val int_minus_mult_eq_1_to_2 =
       
   207     [zmult_zminus, zmult_zminus_right RS sym] MRS trans |> standard;
       
   208 
       
   209 (*to extract again any uncancelled minuses*)
       
   210 val int_minus_from_mult_simps =
       
   211     [zminus_zminus, zmult_zminus, zmult_zminus_right];
       
   212 
       
   213 (*combine unary minus with numeric literals, however nested within a product*)
       
   214 val int_mult_minus_simps =
       
   215     [zmult_assoc, zmult_zminus RS sym, int_minus_mult_eq_1_to_2];
       
   216 
       
   217 fun prep_simproc (name, pats, proc) =
       
   218   Simplifier.simproc (the_context ()) name pats proc;
       
   219 
       
   220 structure CancelNumeralsCommon =
       
   221   struct
       
   222   val mk_sum            = (fn T:typ => mk_sum)
       
   223   val dest_sum          = dest_sum
       
   224   val mk_coeff          = mk_coeff
       
   225   val dest_coeff        = dest_coeff 1
       
   226   val find_first_coeff  = find_first_coeff []
       
   227   fun trans_tac _       = ArithData.gen_trans_tac iff_trans
       
   228 
       
   229   val norm_ss1 = ZF_ss addsimps add_0s @ mult_1s @ diff_simps @ zminus_simps @ zadd_ac
       
   230   val norm_ss2 = ZF_ss addsimps bin_simps @ int_mult_minus_simps @ intifys
       
   231   val norm_ss3 = ZF_ss addsimps int_minus_from_mult_simps @ zadd_ac @ zmult_ac @ tc_rules @ intifys
       
   232   fun norm_tac ss =
       
   233     ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss1))
       
   234     THEN ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss2))
       
   235     THEN ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss3))
       
   236 
       
   237   val numeral_simp_ss = ZF_ss addsimps add_0s @ bin_simps @ tc_rules @ intifys
       
   238   fun numeral_simp_tac ss =
       
   239     ALLGOALS (simp_tac (Simplifier.inherit_context ss numeral_simp_ss))
       
   240     THEN ALLGOALS (SIMPSET' (fn simpset => asm_simp_tac (Simplifier.inherit_context ss simpset)))
       
   241   val simplify_meta_eq  = ArithData.simplify_meta_eq (add_0s @ mult_1s)
       
   242   end;
       
   243 
       
   244 
       
   245 structure EqCancelNumerals = CancelNumeralsFun
       
   246  (open CancelNumeralsCommon
       
   247   val prove_conv = ArithData.prove_conv "inteq_cancel_numerals"
       
   248   val mk_bal   = FOLogic.mk_eq
       
   249   val dest_bal = FOLogic.dest_eq
       
   250   val bal_add1 = eq_add_iff1 RS iff_trans
       
   251   val bal_add2 = eq_add_iff2 RS iff_trans
       
   252 );
       
   253 
       
   254 structure LessCancelNumerals = CancelNumeralsFun
       
   255  (open CancelNumeralsCommon
       
   256   val prove_conv = ArithData.prove_conv "intless_cancel_numerals"
       
   257   val mk_bal   = FOLogic.mk_binrel "Int.zless"
       
   258   val dest_bal = FOLogic.dest_bin "Int.zless" iT
       
   259   val bal_add1 = less_add_iff1 RS iff_trans
       
   260   val bal_add2 = less_add_iff2 RS iff_trans
       
   261 );
       
   262 
       
   263 structure LeCancelNumerals = CancelNumeralsFun
       
   264  (open CancelNumeralsCommon
       
   265   val prove_conv = ArithData.prove_conv "intle_cancel_numerals"
       
   266   val mk_bal   = FOLogic.mk_binrel "Int.zle"
       
   267   val dest_bal = FOLogic.dest_bin "Int.zle" iT
       
   268   val bal_add1 = le_add_iff1 RS iff_trans
       
   269   val bal_add2 = le_add_iff2 RS iff_trans
       
   270 );
       
   271 
       
   272 val cancel_numerals =
       
   273   map prep_simproc
       
   274    [("inteq_cancel_numerals",
       
   275      ["l $+ m = n", "l = m $+ n",
       
   276       "l $- m = n", "l = m $- n",
       
   277       "l $* m = n", "l = m $* n"],
       
   278      K EqCancelNumerals.proc),
       
   279     ("intless_cancel_numerals",
       
   280      ["l $+ m $< n", "l $< m $+ n",
       
   281       "l $- m $< n", "l $< m $- n",
       
   282       "l $* m $< n", "l $< m $* n"],
       
   283      K LessCancelNumerals.proc),
       
   284     ("intle_cancel_numerals",
       
   285      ["l $+ m $<= n", "l $<= m $+ n",
       
   286       "l $- m $<= n", "l $<= m $- n",
       
   287       "l $* m $<= n", "l $<= m $* n"],
       
   288      K LeCancelNumerals.proc)];
       
   289 
       
   290 
       
   291 (*version without the hyps argument*)
       
   292 fun prove_conv_nohyps name tacs sg = ArithData.prove_conv name tacs sg [];
       
   293 
       
   294 structure CombineNumeralsData =
       
   295   struct
       
   296   type coeff            = IntInf.int
       
   297   val iszero            = (fn x : IntInf.int => x = 0)
       
   298   val add               = IntInf.+ 
       
   299   val mk_sum            = (fn T:typ => long_mk_sum) (*to work for #2*x $+ #3*x *)
       
   300   val dest_sum          = dest_sum
       
   301   val mk_coeff          = mk_coeff
       
   302   val dest_coeff        = dest_coeff 1
       
   303   val left_distrib      = left_zadd_zmult_distrib RS trans
       
   304   val prove_conv        = prove_conv_nohyps "int_combine_numerals"
       
   305   fun trans_tac _       = ArithData.gen_trans_tac trans
       
   306 
       
   307   val norm_ss1 = ZF_ss addsimps add_0s @ mult_1s @ diff_simps @ zminus_simps @ zadd_ac @ intifys
       
   308   val norm_ss2 = ZF_ss addsimps bin_simps @ int_mult_minus_simps @ intifys
       
   309   val norm_ss3 = ZF_ss addsimps int_minus_from_mult_simps @ zadd_ac @ zmult_ac @ tc_rules @ intifys
       
   310   fun norm_tac ss =
       
   311     ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss1))
       
   312     THEN ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss2))
       
   313     THEN ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss3))
       
   314 
       
   315   val numeral_simp_ss = ZF_ss addsimps add_0s @ bin_simps @ tc_rules @ intifys
       
   316   fun numeral_simp_tac ss =
       
   317     ALLGOALS (simp_tac (Simplifier.inherit_context ss numeral_simp_ss))
       
   318   val simplify_meta_eq  = ArithData.simplify_meta_eq (add_0s @ mult_1s)
       
   319   end;
       
   320 
       
   321 structure CombineNumerals = CombineNumeralsFun(CombineNumeralsData);
       
   322 
       
   323 val combine_numerals =
       
   324   prep_simproc ("int_combine_numerals", ["i $+ j", "i $- j"], K CombineNumerals.proc);
       
   325 
       
   326 
       
   327 
       
   328 (** Constant folding for integer multiplication **)
       
   329 
       
   330 (*The trick is to regard products as sums, e.g. #3 $* x $* #4 as
       
   331   the "sum" of #3, x, #4; the literals are then multiplied*)
       
   332 
       
   333 
       
   334 structure CombineNumeralsProdData =
       
   335   struct
       
   336   type coeff            = IntInf.int
       
   337   val iszero            = (fn x : IntInf.int => x = 0)
       
   338   val add               = IntInf.*
       
   339   val mk_sum            = (fn T:typ => mk_prod)
       
   340   val dest_sum          = dest_prod
       
   341   fun mk_coeff(k,t) = if t=one then mk_numeral k
       
   342                       else raise TERM("mk_coeff", [])
       
   343   fun dest_coeff t = (dest_numeral t, one)  (*We ONLY want pure numerals.*)
       
   344   val left_distrib      = zmult_assoc RS sym RS trans
       
   345   val prove_conv        = prove_conv_nohyps "int_combine_numerals_prod"
       
   346   fun trans_tac _       = ArithData.gen_trans_tac trans
       
   347 
       
   348 
       
   349 
       
   350 val norm_ss1 = ZF_ss addsimps mult_1s @ diff_simps @ zminus_simps
       
   351   val norm_ss2 = ZF_ss addsimps [zmult_zminus_right RS sym] @
       
   352     bin_simps @ zmult_ac @ tc_rules @ intifys
       
   353   fun norm_tac ss =
       
   354     ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss1))
       
   355     THEN ALLGOALS (asm_simp_tac (Simplifier.inherit_context ss norm_ss2))
       
   356 
       
   357   val numeral_simp_ss = ZF_ss addsimps bin_simps @ tc_rules @ intifys
       
   358   fun numeral_simp_tac ss =
       
   359     ALLGOALS (simp_tac (Simplifier.inherit_context ss numeral_simp_ss))
       
   360   val simplify_meta_eq  = ArithData.simplify_meta_eq (mult_1s);
       
   361   end;
       
   362 
       
   363 
       
   364 structure CombineNumeralsProd = CombineNumeralsFun(CombineNumeralsProdData);
       
   365 
       
   366 val combine_numerals_prod =
       
   367   prep_simproc ("int_combine_numerals_prod", ["i $* j"], K CombineNumeralsProd.proc);
       
   368 
       
   369 end;
       
   370 
       
   371 
       
   372 Addsimprocs Int_Numeral_Simprocs.cancel_numerals;
       
   373 Addsimprocs [Int_Numeral_Simprocs.combine_numerals,
       
   374              Int_Numeral_Simprocs.combine_numerals_prod];
       
   375 
       
   376 
       
   377 (*examples:*)
       
   378 (*
       
   379 print_depth 22;
       
   380 set timing;
       
   381 set trace_simp;
       
   382 fun test s = (Goal s; by (Asm_simp_tac 1));
       
   383 val sg = #sign (rep_thm (topthm()));
       
   384 val t = FOLogic.dest_Trueprop (Logic.strip_assums_concl(getgoal 1));
       
   385 val (t,_) = FOLogic.dest_eq t;
       
   386 
       
   387 (*combine_numerals_prod (products of separate literals) *)
       
   388 test "#5 $* x $* #3 = y";
       
   389 
       
   390 test "y2 $+ ?x42 = y $+ y2";
       
   391 
       
   392 test "oo : int ==> l $+ (l $+ #2) $+ oo = oo";
       
   393 
       
   394 test "#9$*x $+ y = x$*#23 $+ z";
       
   395 test "y $+ x = x $+ z";
       
   396 
       
   397 test "x : int ==> x $+ y $+ z = x $+ z";
       
   398 test "x : int ==> y $+ (z $+ x) = z $+ x";
       
   399 test "z : int ==> x $+ y $+ z = (z $+ y) $+ (x $+ w)";
       
   400 test "z : int ==> x$*y $+ z = (z $+ y) $+ (y$*x $+ w)";
       
   401 
       
   402 test "#-3 $* x $+ y $<= x $* #2 $+ z";
       
   403 test "y $+ x $<= x $+ z";
       
   404 test "x $+ y $+ z $<= x $+ z";
       
   405 
       
   406 test "y $+ (z $+ x) $< z $+ x";
       
   407 test "x $+ y $+ z $< (z $+ y) $+ (x $+ w)";
       
   408 test "x$*y $+ z $< (z $+ y) $+ (y$*x $+ w)";
       
   409 
       
   410 test "l $+ #2 $+ #2 $+ #2 $+ (l $+ #2) $+ (oo $+ #2) = uu";
       
   411 test "u : int ==> #2 $* u = u";
       
   412 test "(i $+ j $+ #12 $+ k) $- #15 = y";
       
   413 test "(i $+ j $+ #12 $+ k) $- #5 = y";
       
   414 
       
   415 test "y $- b $< b";
       
   416 test "y $- (#3 $* b $+ c) $< b $- #2 $* c";
       
   417 
       
   418 test "(#2 $* x $- (u $* v) $+ y) $- v $* #3 $* u = w";
       
   419 test "(#2 $* x $* u $* v $+ (u $* v) $* #4 $+ y) $- v $* u $* #4 = w";
       
   420 test "(#2 $* x $* u $* v $+ (u $* v) $* #4 $+ y) $- v $* u = w";
       
   421 test "u $* v $- (x $* u $* v $+ (u $* v) $* #4 $+ y) = w";
       
   422 
       
   423 test "(i $+ j $+ #12 $+ k) = u $+ #15 $+ y";
       
   424 test "(i $+ j $* #2 $+ #12 $+ k) = j $+ #5 $+ y";
       
   425 
       
   426 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";
       
   427 
       
   428 test "a $+ $-(b$+c) $+ b = d";
       
   429 test "a $+ $-(b$+c) $- b = d";
       
   430 
       
   431 (*negative numerals*)
       
   432 test "(i $+ j $+ #-2 $+ k) $- (u $+ #5 $+ y) = zz";
       
   433 test "(i $+ j $+ #-3 $+ k) $< u $+ #5 $+ y";
       
   434 test "(i $+ j $+ #3 $+ k) $< u $+ #-6 $+ y";
       
   435 test "(i $+ j $+ #-12 $+ k) $- #15 = y";
       
   436 test "(i $+ j $+ #12 $+ k) $- #-15 = y";
       
   437 test "(i $+ j $+ #-12 $+ k) $- #-15 = y";
       
   438 
       
   439 (*Multiplying separated numerals*)
       
   440 Goal "#6 $* ($# x $* #2) =  uu";
       
   441 Goal "#4 $* ($# x $* $# x) $* (#2 $* $# x) =  uu";
       
   442 *)
       
   443