(* Title: tests for rationals

    Author: Walther Neuper

    Use is subject to license terms.

 *)

 "-----------------------------------------------------------------------------";

 "-----------------------------------------------------------------------------";

 "table of contents -----------------------------------------------------------";

 "-----------------------------------------------------------------------------";

 "-------- fun poly_of_term ---------------------------------------------------";

 "-------- fun is_poly --------------------------------------------------------";

 "-------- fun term_of_poly ---------------------------------------------------";

 "-------- integration lev.1 fun factout_p_ -----------------------------------";

 "-------- integration lev.1 fun cancel_p_ ------------------------------------";

 "-------- integration lev.1 fun common_nominator_p_ --------------------------";

 "-------- integration lev.1 fun add_fraction_p_ ------------------------------";

 "-------- and app_rev ...traced down from rewrite_set_ until prepats ---------";

 "-------- fun rewrite_set_ cancel_p downto fun gcd_poly ----------------------";

 "-------- rewrite_set_ cancel_p from: Mathematik 1 Schalk Reniets Verlag -----";

 "-------- rewrite_set_ common_nominator_p from: Mathematik 1 Schalk ----------";

 "-------- integration lev.1 -- lev.5: cancel_p_ & common_nominator_p_ --------";

 "-------- reverse rewrite ----------------------------------------------------";

 "-------- 'reverse-ruleset' cancel_p -----------------------------------------";

 "-------- investigate rls norm_Rational --------------------------------------";

 "-------- examples: rls norm_Rational ----------------------------------------";

 "-------- numeral rationals -----------------------------";

 "-------- cancellation ----------------------------------";

 "-------- common denominator ----------------------------";

 "-------- multiply and cancel ---------------------------";

 "-------- common denominator and multiplication ---------";

 "-------- double fractions ------------------------------";

 "-------- crucial examples ------------------------------";

 "-------- examples for Stefan Karnels thesis ------------";

 "-------- me Schalk I No.186 ----------------------------";

 "-------- interSteps ..Simp_Rat_Double_No-1.xml ---------";

 "-------- interSteps ..Simp_Rat_Cancel_No-1.xml ---------";

 "-------- investigate rulesets for cancel_p -------------";

 "-------- investigate format of factout_ and factout_p_ -";

 "-------- how to stepwise construct Scripts -------------";

 "----------- get_denominator ----------------------------";

 "--------- several errpats in complicated term -------------------";

 "--------------------------------------------------------";

 "-------- nonterminating cancel_p, norm_Rational 2002 ---";

 "--------------------------------------------------------";

 "--------------------------------------------------------";

 "-------- fun poly_of_term ---------------------------------------------------";

 "-------- fun poly_of_term ---------------------------------------------------";

 "-------- fun poly_of_term ---------------------------------------------------";

 val vs = "12 * x^^^3 * y^^^4 * z^^^6" |> str2term |> vars |> map free2str |> sort string_ord;

 if poly_of_term vs (str2term "12::real") = SOME [(12, [0, 0, 0])]

 then () else error "poly_of_term 1 changed";

 if poly_of_term vs (str2term "x::real") = SOME [(1, [1, 0, 0])]

 then () else error "poly_of_term 2 changed";

 if poly_of_term vs (str2term "12 * x^^^3") = SOME [(12, [3, 0, 0])]

 then () else error "poly_of_term 3 changed";

 if poly_of_term vs (str2term "12 * x^^^3 * y^^^4 * z^^^6") = SOME [(12, [3, 4, 6])]

 then () else error "poly_of_term 4 changed";

 if poly_of_term vs (str2term "1 + 2 * x^^^3 * y^^^4 * z^^^6 + y") =

   SOME [(1, [0, 0, 0]), (1, [0, 1, 0]), (2, [3, 4, 6])]

 then () else error "poly_of_term 5 changed";

 (*poly_of_term is quite liberal:*)

 (*the coefficient may be somewhere, the order of variables and the parentheses 

   within a monomial are arbitrary*)

 if poly_of_term vs (str2term "y^^^4 * (x^^^3 * 12 * z^^^6)") = SOME [(12, [3, 4, 6])]

 then () else error "poly_of_term 6 changed";

 (*there may even be more than 1 coefficient:*)

 if poly_of_term vs (str2term "2 * y^^^4 * (x^^^3 * 6 * z^^^6)") = SOME [(12, [3, 4, 6])]

 then () else error "poly_of_term 7 changed";

 (*the order and the parentheses within monomials are arbitrary:*)

 if poly_of_term vs (str2term "2 * x^^^3 * y^^^4 * z^^^6 + (7 * y^^^8 + 1)")

   = SOME [(1, [0, 0, 0]), (7, [0, 8, 0]), (2, [3, 4, 6])]

 then () else error "poly_of_term 8 changed";

 "-------- fun is_poly --------------------------------------------------------";

 "-------- fun is_poly --------------------------------------------------------";

 "-------- fun is_poly --------------------------------------------------------";

 if is_poly (str2term "2 * x^^^3 * y^^^4 * z^^^6 + 7 * y^^^8 + 1")

 then () else error "is_poly 1 changed";

 if not (is_poly (str2term "2 * (x^^^3 * y^^^4 * z^^^6 + 7) * y^^^8 + 1"))

 then () else error "is_poly 2 changed";

 "-------- fun term_of_poly ---------------------------------------------------";

 "-------- fun term_of_poly ---------------------------------------------------";

 "-------- fun term_of_poly ---------------------------------------------------";

 val expT = HOLogic.realT

 val Free (_, baseT) = (hd o vars o str2term) "12 * x^^^3 * y^^^4 * z^^^6";

 val p = [(1, [0, 0, 0]), (7, [0, 8, 0]), (2, [3, 4, 5])]

 val vs = ["x","y","z"]

 (*precondition for [(c, es),...]: legth es = length vs*)

 ;

 if term2str (term_of_poly baseT expT vs p) = "1 + 7 * y ^^^ 8 + 2 * x ^^^ 3 * y ^^^ 4 * z ^^^ 5"

 then () else error "term_of_poly 1 changed";

 "-------- integration lev.1 fun factout_p_ -----------------------------------";

 "-------- integration lev.1 fun factout_p_ -----------------------------------";

 "-------- integration lev.1 fun factout_p_ -----------------------------------";

 val t = str2term "(x^^^2 + -1*y^^^2) / (x^^^2 + -1*x*y)"

 val SOME (t', asm) = factout_p_ thy t;

 if term2str t' = "(x + y) * (x + -1 * y) / (x * (x + -1 * y))"

 then () else error ("factout_p_ term 1 changed: " ^ term2str t')

 ;

 if terms2str asm = "[\"x ~= 0\",\"x + -1 * y ~= 0\"]"

 then () else error "factout_p_ asm 1 changed"

 ;

 val t = str2term "nothing + to_cancel ::real";

 if NONE = factout_p_ thy t then () else error "factout_p_ doesn't report non-applicable";

 ;

 val t = str2term "((3 * x^^^2 + 6 *x + 3) / (2*x + 2))";

 val SOME (t', asm) = factout_p_ thy t;

 if term2str t' = "(3 + 3 * x) * (1 + x) / (2 * (1 + x))" andalso 

   terms2str asm = "[\"1 + x ~= 0\"]"

 then () else error "factout_p_ 1 changed";

 "-------- integration lev.1 fun cancel_p_ ------------------------------------";

 "-------- integration lev.1 fun cancel_p_ ------------------------------------";

 "-------- integration lev.1 fun cancel_p_ ------------------------------------";

 val t = str2term "(x^^^2 + -1*y^^^2) / (x^^^2 + -1*x*y)"

 val SOME (t', asm) = cancel_p_ thy t;

 if (term2str t', terms2str asm) = ("(x + y) / x", "[\"x ~= 0\"]")

 then () else error ("cancel_p_ (t', asm) 1 changed: " ^ term2str t')

 ;

 val t = str2term "nothing + to_cancel ::real";

 if NONE = cancel_p_ thy t then () else error "cancel_p_ doesn't report non-applicable";

 ;

 val t = str2term "((3 * x^^^2 + 6 *x + 3) / (2*x + 2))";

 val SOME (t', asm) = cancel_p_ thy t;

 if term2str t' = "(3 + 3 * x) / 2" andalso terms2str asm = "[]"

 then () else error "cancel_p_ 1 changed";

 "-------- integration lev.1 fun common_nominator_p_ --------------------------";

 "-------- integration lev.1 fun common_nominator_p_ --------------------------";

 "-------- integration lev.1 fun common_nominator_p_ --------------------------";

 val t = str2term ("y / (a*x + b*x + c*x) " ^

               (* n1    d1                   *)

                 "+ a / (x*y)");

               (* n2    d2                   *)

 val SOME (t', asm) = common_nominator_p_ thy t;

 if term2str t' =

       ("y * y / (x * ((a + b + c) * y)) " ^

   (*  n1  *d2'/ (c'* ( d1'        *d2')) *)

      "+ a * (a + b + c) / (x * ((a + b + c) * y))")

    (*  n2 * d1'         / (c'* ( d1'        *d2')) *)

 then () else error "common_nominator_p_ term 1 changed";

 if terms2str asm = "[\"a + b + c ~= 0\",\"y ~= 0\",\"x ~= 0\"]"

 then () else error "common_nominator_p_ asm 1 changed"

 "-------- example in mail Nipkow";

 val t = str2term "x/(x^^^2 + -1*y^^^2) + y/(x^^^2 + -1*x*y)";

 val SOME (t', asm) = common_nominator_p_ thy t;

 if term2str t' = "x * x / " ^ 

                  "((x + -1 * y) * ((x + y) * x))" ^

             " +\n" ^ 

                  "y * (x + y) / " ^ 

                  "((x + -1 * y) * ((x + y) * x))"

 then () else error "common_nominator_p_ term 2 changed"

 ;

 if terms2str asm = "[\"x + y ~= 0\",\"x ~= 0\",\"x + -1 * y ~= 0\"]"

 then () else error "common_nominator_p_ asm 2 changed"

 "-------- example: applicable tested by SML code";

 val t = str2term "nothing / to_add";

 if NONE = common_nominator_p_ thy t then () else error "common_nominator_p_ term 3 changed";

 ;

 val t = str2term "((x + (-1)) / (x + 1)) + ((x + 1) / (x + (-1)))";

 val SOME (t', asm) = common_nominator_p_ thy t;

 if term2str t' = 

    "(x + -1) * (-1 + x) / ((1 + x) * (-1 + x)) +\n(x + 1) * (1 + x) / ((1 + x) * (-1 + x))"

   andalso terms2str asm = "[\"1 + x ~= 0\",\"-1 + x ~= 0\"]"

 then () else error "common_nominator_p_ 3 changed";

 "-------- integration lev.1 fun add_fraction_p_ ------------------------------";

 "-------- integration lev.1 fun add_fraction_p_ ------------------------------";

 "-------- integration lev.1 fun add_fraction_p_ ------------------------------";

 val t = str2term "((x + (-1)) / (x + 1)) + ((x + 1) / (x + (-1)))";

 val SOME (t', asm) = add_fraction_p_ thy t;

 if term2str t' = "(2 + 2 * x ^^^ 2) / (-1 + x ^^^ 2)" 

 then () else error "add_fraction_p_ 3 changed";

 ;

 if terms2str asm = "[\"-1 + x ^^^ 2 ~= 0\"]"

 then () else error "add_fraction_p_ 3 changed";

 ;

 val t = str2term "nothing / to_add";

 if NONE = add_fraction_p_ thy t then () else error "add_fraction_p_ term 3 changed";

 ;

 val t = str2term "((x + (-1)) / (x + 1)) + ((x + 1) / (x + (-1)))";

 val SOME (t', asm) = add_fraction_p_ thy t;

 if term2str t' = "(2 + 2 * x ^^^ 2) / (-1 + x ^^^ 2)" andalso

   terms2str asm = "[\"-1 + x ^^^ 2 ~= 0\"]"

 then () else error "add_fraction_p_ 3 changed";

 "-------- and app_rev ...traced down from rewrite_set_ until prepats ---------";

 "-------- and app_rev ...traced down from rewrite_set_ until prepats ---------";

 "-------- and app_rev ...traced down from rewrite_set_ until prepats ---------";

 (* trace down until prepats are evaluated 

   (which does not to work, because substitution is not done -- compare rew_sub!);

   keep this sequence for the case, factout_p, cancel_p, common_nominator_p, add_fraction_p

   (again) get prepat = [] changed to <>[]. *)

 val t = str2term "(x^^^2 + -1*y^^^2) / (x^^^2 + -1*x*y)";

 (*rewrite_set_ @{theory Isac} true cancel t = NONE; !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ fun rewrite_set_, args:"; val (thy, bool, rls, term) = (thy, false, cancel_p, t);

 "~~~~~ fun rewrite__set_, args:"; val (thy, i, _, _, (rrls as Rrls _), t) =

   (thy, 1, bool, [], rls, term);

 (*val (t', asm, rew) = app_rev thy (i+1) rrls t; rew = false!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ and app_rev, args:"; val (thy, i, rrls, t) = (thy, (i+1), rrls, t);

     fun chk_prepat thy erls [] t = true

       | chk_prepat thy erls prepat t =

         let

           fun chk (pres, pat) =

             (let 

               val subst: Type.tyenv * Envir.tenv =

                 Pattern.match thy (pat, t) (Vartab.empty, Vartab.empty)

              in

               snd (eval__true thy (i + 1) (map (Envir.subst_term subst) pres) [] erls)

              end) handle _ => false

            fun scan_ f [] = false (*scan_ NEVER called by []*)

              | scan_ f (pp::pps) =

                if f pp then true else scan_ f pps;

         in scan_ chk prepat end;

     (* apply the normal_form of a rev-set *)

     fun app_rev' thy (Rrls{erls,prepat,scr=Rfuns{normal_form,...},...}) t =

       if chk_prepat thy erls prepat t

       then ((*tracing("### app_rev': t = "^(term2str t));*) normal_form t)

       else NONE;

 (*  val opt = app_rev' thy rrls t  ..NONE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ and app_rev', args:"; val (thy, (Rrls{erls,prepat,scr=Rfuns{normal_form,...},...}), t) =

   (thy, rrls, t);

 (* chk_prepat thy erls prepat t = false!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 (* app_sub thy i rrls t = false!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ fun chk_prepat, args:"; val (thy, erls, prepat, t) = (thy, erls, prepat, t);

           fun chk (pres, pat) =

             (let 

               val subst: Type.tyenv * Envir.tenv =

                 Pattern.match thy (pat, t) (Vartab.empty, Vartab.empty)

              in

               snd (eval__true thy (i + 1) (map (Envir.subst_term subst) pres) [] erls)

              end) handle _ => false

            fun scan_ f [] = false (*scan_ NEVER called by []*)

              | scan_ f (pp::pps) =

                if f pp then true else scan_ f pps;

 (*========== inhibit exn WN130823: prepat is empty ====================================

 (* scan_ chk prepat = false!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ fun , args:"; val (f, (pp::pps)) = (chk, prepat);

 f;

 val ([t1, t2], t) = pp;

 term2str t1 = "?r is_expanded";

 term2str t2 = "?s is_expanded";

 term2str t = "?r / ?s";

 (* f pp = false!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

 "~~~~~ fun chk, args:"; val (pres, pat) = (pp);

               val subst: Type.tyenv * Envir.tenv =

                 Pattern.match thy (pat, t) (Vartab.empty, Vartab.empty)

 (*subst = 

   ({}, {(("r", 0), ("real", Var (("r", 0), "real"))), 

         (("s", 0), ("real", Var (("s", 0), "real")))}*)

 ;

               snd (eval__true thy (i + 1) (map (Envir.subst_term subst) pres) [] erls)

 "~~~~~ fun eval__true, args:"; val (thy, i, asms, bdv, rls) =

   (thy, (i + 1), (map (Envir.subst_term subst) pres), [], erls);

 terms2str asms;                         (* = "[\"?r is_expanded\",\"?s is_expanded\"]"*)

 asms = [@{term True}] orelse asms = []; (* = false*)

 asms = [@{term False}]                ; (* = false*)

 "~~~~~ fun chk, args:"; val (indets, (a::asms)) = ([], asms);

 bdv (*= []: _a list*);

 val bdv : (term * term) list = [];

 rewrite__set_ thy (i+1) false;

 term2str a = "?r is_expanded"; (*hier m"usste doch der Numerator eingesetzt sein ??????????????*)

 val SOME (Const ("HOL.False", _), []) = rewrite__set_ thy (i+1) false bdv rls a

 ============ inhibit exn WN130823: prepat is empty ===================================*)

 "-------- fun rewrite_set_ cancel_p downto fun gcd_poly ----------------------";

 "-------- fun rewrite_set_ cancel_p downto fun gcd_poly ----------------------";

 "-------- fun rewrite_set_ cancel_p downto fun gcd_poly ----------------------";

 val t = str2term "(12 * x * y) / (8 * y^^^2 )";

 (* "-------- example 187a": exception Div raised...

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;*)

 val t = str2term "(8 * x^^^2 * y * z ) / (18 * x * y^^^2 * z )";

 (* "-------- example 187b": doesn't terminate...

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;*)

 val t = str2term "(9 * x^^^5 * y^^^2 * z^^^4) / (15 * x^^^6 * y^^^3 * z )";

 (* "-------- example 187c": doesn't terminate...

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;*)

 "~~~~~ fun rewrite_set_, args:"; val (thy, bool, rls, term) = (@{theory Isac}, false, cancel_p, t);

 (* WN130827: exception Div raised...

 rewrite__set_ thy 1 bool [] rls term

 *)

 "~~~~~ and rewrite__set_, args:"; val (thy, i, _, _, (rrls as Rrls _), t) =

   (thy, 1, bool, [], rls, term);

 (* WN130827: exception Div raised...

 	val (t', asm, rew) = app_rev thy (i+1) rrls t

 *)

 "~~~~~ fun app_rev, args:"; val (thy, i, rrls, t) = (thy, (i+1), rrls, t);

 (* WN130827: exception Div raised...

     val opt = app_rev' thy rrls t

 *)

 "~~~~~ fun app_rev', args:"; val (thy, (Rrls{erls,prepat,scr=Rfuns{normal_form,...},...}), t) =

   (thy, rrls, t);

 chk_prepat thy erls prepat t    = true;

 (* WN130827: exception Div raised...

 normal_form t

 *)

 (* lookup Rational.thy, cancel_p: normal_form = cancel_p_ thy*)

 "~~~~~ fun cancel_p_, args:"; val (t) = (t);

 val opt = check_fraction t;

 val SOME (numerator, denominator) = opt

         val vs = t |> vars |> map free2str |> sort string_ord

         val baseT = type_of numerator

         val expT = HOLogic.realT

 val (SOME a, SOME b) = (poly_of_term vs numerator, poly_of_term vs denominator);

 (*"-------- example 187a": exception Div raised...

 val a = [(12, [1, 1])]: poly

 val b = [(8, [0, 2])]: poly

               val ((a', b'), c) = gcd_poly a b

 *)

 (* "-------- example 187b": doesn't terminate...

 val a = [(8, [2, 1, 1])]: poly

 val b = [(18, [1, 2, 1])]: poly

               val ((a', b'), c) = gcd_poly a b

 *)

 (* "-------- example 187c": doesn't terminate...

 val a = [(9, [5, 2, 4])]: poly

 val b = [(15, [6, 3, 1])]: poly

               val ((a', b'), c) = gcd_poly a b

 *)

 "-------- rewrite_set_ cancel_p from: Mathematik 1 Schalk Reniets Verlag -----";

 "-------- rewrite_set_ cancel_p from: Mathematik 1 Schalk Reniets Verlag -----";

 "-------- rewrite_set_ cancel_p from: Mathematik 1 Schalk Reniets Verlag -----";

 val thy  = @{theory "Rational"};

 "-------- WN";

 val t = str2term "(2 + -3 * x) / 9";

 if NONE = rewrite_set_ thy false cancel_p t then ()

 else error "rewrite_set_ cancel_p must return NONE, if the term cannot be cancelled";

 "-------- example 186a";

 val t = str2term "(14 * x * y) / (x * y)";

   is_expanded (str2term "14 * x * y");

   is_expanded (str2term "x * y");

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("14 / 1", "[]")

 then () else error "rational.sml cancel Schalk 186a";

 "-------- example 186b";

 val t = str2term "(60 * a * b) / ( 15 * a  * b )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("4 / 1", "[]")

 then () else error "rational.sml cancel Schalk 186b";

 "-------- example 186c";

 val t = str2term "(144 * a^^^2 * b * c) / (12 * a * b * c)";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("12 * a / 1", "[]")

 then () else error "rational.sml cancel Schalk 186c";

 (* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! exception Div raised !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

   see --- fun rewrite_set_ downto fun gcd_poly ---

 "-------- example 187a";

 val t = str2term "(12 * x * y) / (8 * y^^^2 )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("3 * x / (2 * y)", "[\"4 * y ~= 0\"]")

 then () else error "rational.sml cancel Schalk 187a";

 *)

 (* doesn't terminate !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

   see --- fun rewrite_set_ downto fun gcd_poly ---

 "-------- example 187b";

 val t = str2term "(8 * x^^^2 * y * z ) / (18 * x * y^^^2 * z )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("4 * x / (9 * y)", "[\"2 * (z * (y * x)) ~= 0\"]")

 then () else error "rational.sml cancel Schalk 187b";

 *)

 (* doesn't terminate !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

   see --- fun rewrite_set_ downto fun gcd_poly ---

 "-------- example 187c";

 val t = str2term "(9 * x^^^5 * y^^^2 * z^^^4) / (15 * x^^^6 * y^^^3 * z )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = 

   ("3 * z ^^^ 3 / (5 * (y * x))", "[\"3 * (z * (y ^^^ 2 * x ^^^ 5)) ~= 0\"]") 

 then () else error "rational.sml cancel Schalk 187c";

 *)

 "-------- example 188a";

 val t = str2term "(-8 + 8 * x) / (-9 + 9 * x)";

   is_expanded (str2term "8 * x + -8");

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("8 / 9", "[]")

 then () else error "rational.sml cancel Schalk 188a";

 val t = str2term "(8*((-1) + x))/(9*((-1) + x))";

 val SOME (t,_) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = ("8 / 9", "[]")

 then () else error "rational.sml cancel Schalk make_polynomial 1";

 "-------- example 188b";

 val t = str2term "(-15 + 5 * x) / (-18 + 6 * x)";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("5 / 6", "[]")

 then () else error "rational.sml cancel Schalk 188b";

 "-------- example 188c";

 val t = str2term "(a + -1 * b) / (b + -1 * a)";

 val SOME (t', asm) = rewrite_set_ thy false  cancel_p t;

 if (term2str t', terms2str asm) = ("-1 / 1", "[]")

 then () else error "rational.sml cancel Schalk 188c";

 is_expanded (str2term "a + -1 * b") = true;

 val t = str2term "((-1)*(b + (-1) * a))/(1*(b + (-1) * a))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = ("(a + -1 * b) / (-1 * a + b)", "[]")

 then () else error "rational.sml cancel Schalk make_polynomial 2";

 "-------- example 190a";

 val t = str2term "( 27 * a^^^3 + 9 * a^^^2 + 3 * a + 1 ) / ( 27 * a^^^3 + 18 * a^^^2 + 3 * a )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = 

   ("(1 + 9 * a ^^^ 2) / (3 * a + 9 * a ^^^ 2)", "[\"3 * a + 9 * a ^^^ 2 ~= 0\"]")

 then () else error "rational.sml cancel Schalk 190a";

 "-------- example 190c";

 val t = str2term "((1 + 9 * a ^^^ 2)*(1 + 3 * a))/((3 * a + 9 * a ^^^ 2)*(1 + 3 * a))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = 

   ("(1 + 3 * a + 9 * a ^^^ 2 + 27 * a ^^^ 3) /\n(3 * a + 18 * a ^^^ 2 + 27 * a ^^^ 3)", "[]")

 then () else error "rational.sml make_polynomial Schalk 190c";

 "-------- example 191a";

 val t = str2term "( x^^^2 + -1 * y^^^2 ) / ( x + y )";

   is_expanded (str2term "x^^^2 + -1 * y^^^2") = false; (*!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*)

   is_expanded (str2term "x + y") = true;

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("(x + -1 * y) / 1", "[]")

 then () else error "rational.sml make_polynomial Schalk 191a";

 "-------- example 191b";

 val t = str2term "((x + (-1) * y)*(x + y))/((1)*(x + y))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = ("(x ^^^ 2 + -1 * y ^^^ 2) / (x + y)", "[]")

 then () else error "rational.sml make_polynomial Schalk 191b";

 "-------- example 191c";

 val t = str2term "( 9 * x^^^2 + -30 * x + 25 ) / ( 9 * x^^^2 + -25 )";

   is_expanded (str2term "9 * x^^^2 + -30 * x + 25") = true;

   is_expanded (str2term "25 + -30*x + 9*x^^^2") = true;

   is_expanded (str2term "-25 + 9*x^^^2") = true;

 val t = str2term "(((-5) + 3 * x)*((-5) + 3 * x))/((5 + 3 * x)*((-5) + 3 * x))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = ("(25 + -30 * x + 9 * x ^^^ 2) / (-25 + 9 * x ^^^ 2)", "[]")

 then () else error "rational.sml make_polynomial Schalk 191c";

 "-------- example 192b";

 val t = str2term "( 7 * x^^^3 + -1 * x^^^2 * y ) / ( 7 * x * y^^^2 + -1 *  y^^^3 )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("x ^^^ 2 / y ^^^ 2", "[\"y ^^^ 2 ~= 0\"]")

 then () else error "rational.sml cancel_p Schalk 192b";

 val t = str2term "((x ^^^ 2)*(7 * x + (-1) * y))/((y ^^^ 2)*(7 * x + (-1) * y))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = 

   ("(7 * x ^^^ 3 + -1 * x ^^^ 2 * y) / (7 * x * y ^^^ 2 + -1 * y ^^^ 3)", "[]")

 then () else error "rational.sml make_polynomial Schalk 192b";

 val t = str2term "((x ^^^ 2)*(7 * x + (-1) * y))/((y ^^^ 2)*(7 * x + (-1) * y))";

 val SOME (t', asm) = rewrite_set_ thy false make_polynomial t;

 if (term2str t', terms2str asm) = 

   ("(7 * x ^^^ 3 + -1 * x ^^^ 2 * y) / (7 * x * y ^^^ 2 + -1 * y ^^^ 3)", "[]")

 then () else error "rational.sml make_polynomial Schalk WN050929 not working";

 "-------- example 193a";

 val t = str2term "( x^^^2 + -6 * x + 9 ) / ( x^^^2 + -9 )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("(-3 + x) / (3 + x)", "[\"3 + x ~= 0\"]")

 then () else error "rational.sml cancel_p Schalk 193a";

 "-------- example 193b";

 val t = str2term "( x^^^2 + -8 * x + 16 ) / ( 2 * x^^^2 + -32 )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("(-4 + x) / (8 + 2 * x)", "[\"8 + 2 * x ~= 0\"]")

 then () else error "rational.sml cancel_p Schalk 193b";

 "-------- example 193c";

 val t = str2term "( 2 * x + -50 * x^^^3 ) / ( 25 * x^^^2 + -10 * x + 1 )";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = 

   ("(2 * x + 10 * x ^^^ 2) / (1 + -5 * x)", "[\"1 + -5 * x ~= 0\"]")

 then () else error "rational.sml cancel_p Schalk 193c";

 (*WN:*)

 val t = str2term "(-25 + 9*x^^^2)/(5 + 3*x)";

 val SOME (t, asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = ("(2 * x + 10 * x ^^^ 2) / (1 + -5 * x)", "[]")

 then () else error "rational.sml cancel WN 1";

 "-------- example heuberger";

 val t = str2term ("(x^^^4 + x * y + x^^^3 * y + y^^^2) / " ^

   "(x + 5 * x^^^2 + y + 5 * x * y + x^^^2 * y^^^3 + x * y^^^4)");

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if (term2str t', terms2str asm) = 

   ("(x ^^^ 3 + y) / (1 + 5 * x + x * y ^^^ 3)", "[\"1 + 5 * x + x * y ^^^ 3 ~= 0\"]")

 then () else error "rational.sml cancel_p heuberger";

 "-------- rewrite_set_ common_nominator_p from: Mathematik 1 Schalk ----------";

 "-------- rewrite_set_ common_nominator_p from: Mathematik 1 Schalk ----------";

 "-------- rewrite_set_ common_nominator_p from: Mathematik 1 Schalk ----------";

 (*deleted example 204 ... 236b at update Isabelle2012-->2013*)

 "-------- integration lev.1 -- lev.5: cancel_p_ & common_nominator_p_ --------";

 "-------- integration lev.1 -- lev.5: cancel_p_ & common_nominator_p_ --------";

 "-------- integration lev.1 -- lev.5: cancel_p_ & common_nominator_p_ --------";

 val t = str2term ("123 = (a*x)/(b*x) + (c*x)/(d*x) + (e*x)/(f*x::real)");

 "-------- gcd_poly integration level 1: works on exact term";

 if NONE = cancel_p_ thy t then () else error "cancel_p_ works on exact fraction";

 if NONE = add_fraction_p_ thy t then () else error "add_fraction_p_ works on exact fraction";

 "-------- gcd_poly integration level 2: picks out ONE appropriate subterm";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p t;

 if term2str t' = "123 = a * x / (b * x) + c * x / (d * x) + e / f" 

 then () else error "level 2, rewrite_set_ cancel_p: changed";

 val SOME (t', asm) = rewrite_set_ thy false add_fractions_p t;

 if term2str t' = "123 = (b * c * x + a * d * x) / (b * d * x) + e * x / (f * x)"

 then () else error "level 2, rewrite_set_ add_fractions_p: changed";

 "-------- gcd_poly integration level 3: rewrites all appropriate subterms";

 val SOME (t', asm) = rewrite_set_ thy false cancel_p_rls t;

 if term2str t' = "123 = a / b + c / d + e / f"

 then () else error "level 3, rewrite_set_ cancel_p_rls: changed";

 val SOME (t', asm) = rewrite_set_ thy false common_nominator_p_rls t; (*CREATE add_fractions_p_rls*)

 if term2str t' = "123 = (b * d * e * x + b * c * f * x + a * d * f * x) / (b * d * f * x)"

 then () else error "level 3, rewrite_set_ add_fractions_p_rls: changed";

 "-------- gcd_poly integration level 4: iteration cancel_p -- add_fraction_p";

 (* simpler variant *)

 val testrls = append_rls "testrls" e_rls [Rls_ cancel_p, Rls_ add_fractions_p]

 val SOME (t', asm) = rewrite_set_ thy false testrls t;

 (*trace_rewrite := false;

 #  rls: testrls on: 123 = a * x / (b * x) + c * x / (d * x) + e * x / (f * x) 

 ##  rls: cancel_p on: 123 = a * x / (b * x) + c * x / (d * x) + e * x / (f * x) 

 ##  rls: common_nominator_p on: 123 = a * x / (b * x) + c * x / (d * x) + e / f 

 ##  rls: cancel_p on: 123 = (b * c * x + a * d * x) / (b * d * x) + e / f 

 ##  rls: common_nominator_p on: 123 = (b * c + a * d) / (b * d) + e / f 

 ##  rls: cancel_p on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) 

 ##  rls: common_nominator_p on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) *)

 if term2str t' = "123 = (b * d * e + b * c * f + a * d * f) / (b * d * f)"

 then () else error "level 4, rewrite_set_ *_p: changed";

 (* complicated variant *)

 val testrls_rls = append_rls "testrls_rls" e_rls [Rls_ cancel_p_rls, Rls_ common_nominator_p_rls];

 val SOME (t', asm) = rewrite_set_ thy false testrls_rls t;

 (*#  rls: testrls_rls on: 123 = a * x / (b * x) + c * x / (d * x) + e * x / (f * x) 

 ##  rls: cancel_p_rls on: 123 = a * x / (b * x) + c * x / (d * x) + e * x / (f * x) 

 ###  rls: cancel_p on: 123 = a * x / (b * x) + c * x / (d * x) + e * x / (f * x) 

 ###  rls: cancel_p on: 123 = a * x / (b * x) + c * x / (d * x) + e / f 

 ###  rls: cancel_p on: 123 = a * x / (b * x) + c / d + e / f 

 ###  rls: cancel_p on: 123 = a / b + c / d + e / f 

 ##  rls: common_nominator_p_rls on: 123 = a / b + c / d + e / f 

 ###  rls: common_nominator_p on: 123 = a / b + c / d + e / f 

 ###  rls: common_nominator_p on: 123 = (b * c + a * d) / (b * d) + e / f 

 ###  rls: common_nominator_p on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) 

 ##  rls: cancel_p_rls on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) 

 ###  rls: cancel_p on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) 

 ##  rls: common_nominator_p_rls on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) 

 ###  rls: common_nominator_p on: 123 = (b * d * e + b * c * f + a * d * f) / (b * d * f) *)

 if term2str t' = "123 = (b * d * e + b * c * f + a * d * f) / (b * d * f)"

 then () else error "level 4, rewrite_set_ *_p_rls: changed"

 "-------- gcd_poly integration level 5: cancel_p & add_fraction_p within norm_Rational";

 val SOME (t', asm) = rewrite_set_ thy false norm_Rational t;

 if term2str t' = "123 = (a * d * f + b * c * f + b * d * e) / (b * d * f)"

 then () else error "level 5, rewrite_set_ norm_Rational: changed"

 "-------- reverse rewrite ----------------------------------------------------";

 "-------- reverse rewrite ----------------------------------------------------";

 "-------- reverse rewrite ----------------------------------------------------";

 (** the term for which reverse rewriting is demonstrated **)

 val t = str2term "(9 + -1 * x ^^^ 2) / (9 + 6 * x + x ^^^ 2)";

 val Rrls {scr = Rfuns {init_state = ini, locate_rule = loc,

   next_rule = nex, normal_form = nor, ...},...} = cancel_p;

 (** normal_form produces the result in ONE step **)

   val SOME (t',_) = nor t;

 if term2str t' = "(3 + -1 * x) / (3 + x)" then ()

 else error "rational.sml normal_form (9 - x ^^^ 2) / (9 - 6 * x + x ^^^ 2)";

 (** initialize the interpreter state used by the 'me' **)

   val (t, _, revsets, _) = ini t;

 if length (hd revsets) = 11 then () else error "length of revset changed";

 if (revsets |> nth 1 |> nth 1 |> id_of_thm) = 

   (@{thm realpow_twoI} |> string_of_thm |> thmID_of_derivation_name)

 then () else error "first element of revset changed";

 if

 (revsets |> nth 1 |> nth 1 |> rule2str) = "Thm (\"realpow_twoI\",??.unknown)" andalso

 (revsets |> nth 1 |> nth 2 |> rule2str) = 

   "Thm (\"sym_#power_Float ((3,0), (0,0)) __ ((2,0), (0,0))\",??.unknown)" andalso

 (revsets |> nth 1 |> nth 3 |> rule2str) = 

   "Thm (\"sym_#mult_Float ((2,0), (0,0)) __ ((3,0), (0,0))\",??.unknown)" andalso

 (revsets |> nth 1 |> nth 4 |> rule2str) = 

   "Thm (\"sym_#mult_Float ((~1,0), (0,0)) __ ((3,0), (0,0))\",??.unknown)" andalso

 (revsets |> nth 1 |> nth 5 |> rule2str) = 

   "Thm (\"sym_#mult_Float ((3,0), (0,0)) __ ((3,0), (0,0))\",??.unknown)" andalso

 (revsets |> nth 1 |> nth 6 |> rule2str) = "Rls_ (\"sym_order_mult_rls_\")" andalso

 (revsets |> nth 1 |> nth 7 |> rule2str) = 

   "Thm (\"sym_mult_assoc\",Groups.semigroup_mult_class.mult_assoc)"

 then () else error "first 7 elements in revset changed"

 (** find the rule 'r' to apply to term 't' **)

 (*/------- since cancel_ (accepted "-" between monomials) has been replaced by cancel_p_ 

   for Isabelle2013, we don't get a working revset, but non-termination:

   val SOME (r as (Thm (str, thm))) = nex revsets t;

   :

 ((3 * 3 + -1 * x * x) / (3 * 3 + 2 * 3 * x + x * x), 

   Rls_ ("sym_order_mult_rls_"), ((3 * 3 + -1 * (x * x)) / (3 * 3 + 2 * (3 * x) + x * x), []))","

 ((3 * 3 + -1 * (x * x)) / (3 * 3 + 2 * (3 * x) + x * x), 

   Thm ("sym_mult_assoc",""), ((3 * 3 + -1 * (x * x)) / (3 * 3 + 2 * 3 * x + x * x), []))","

 ((3 * 3 + -1 * (x * x)) / (3 * 3 + 2 * 3 * x + x * x), 

   Thm ("sym_mult_assoc",""), ((3 * 3 + -1 * x * x) / (3 * 3 + 2 * 3 * x + x * x), []))","

 ((3 * 3 + -1 * x * x) / (3 * 3 + 2 * 3 * x + x * x), Rls_ ("sym_order_mult_rls_"), ((3 * 3 + -1 * (x * x)) / (3 * 3 + 2 * (3 * x) + x * x), []))","

  :

 ### Isabelle2002:

   Thm ("sym_#mult_2_3", "6 = 2 * 3")

 ### Isabelle2009-2 for cancel_ (not cancel_p_):

 if str = "sym_#power_Float ((3,0), (0,0)) __ ((2,0), (0,0))"

    andalso string_of_thm thm = 

            (string_of_thm o make_thm o (cterm_of (@{theory "Isac"})))

                (Trueprop $ (term_of o the o (parse thy)) "9 = 3 ^^^ 2") then ()

 else error "rational.sml next_rule (9 - x ^^^ 2) / (9 - 6 * x + x ^^^ 2)";

 \---------------------------------------------------------------------------------------/*)

 (** check, if the rule 'r' applied by the user to 't' belongs to the ruleset;

   if the rule is OK, the term resulting from applying the rule is returned,too;

   there might be several rule applications inbetween,

   which are listed after the head in reverse order **)

 (*/-------------------------------------------- Isabelle2013: this gives "error id_of_thm";

   we don't repair this, because interaction within "reverse rewriting" never worked properly:

   val (r, (t, asm))::_ = loc revsets t r;

 if term2str t = "(9 - x ^^^ 2) / (3 ^^^ 2 + 6 * x + x ^^^ 2)" andalso asm = []

 then () else error "rational.sml locate_rule (9 - x ^^^ 2) / (9 - 6 * x + x ^^^ 2)";

 (* find the next rule to apply *)

   val SOME (r as (Thm (str, thm))) = nex revsets t;

 if str = "sym_#power_Float ((3,0), (0,0)) __ ((2,0), (0,0))" andalso

    string_of_thm thm = (string_of_thm o make_thm o (cterm_of (@{theory "Isac"})))

                 (Trueprop $ (term_of o the o (parse thy)) "9 = 3 ^^^ 2") then ()

 else error "rational.sml next_rule (9 - x ^^^ 2) / (9 - 6 * x + x ^^^ 2)";

 (*check the next rule*)

   val (r, (t, asm)) :: _ = loc revsets t r;

 if term2str t = "(3 ^^^ 2 - x ^^^ 2) / (3 ^^^ 2 + 6 * x + x ^^^ 2)" then ()

 else error "rational.sml locate_rule (9 - x ^^^ 2) / (9 - 6 * x + x ^^^ 2) II";

 (*find and check the next rules, rewrite*)

   val SOME r = nex revsets t;

   val (r,(t,asm))::_ = loc revsets t r;

 if term2str t = "(3 ^^^ 2 - x ^^^ 2) / (3 ^^^ 2 + 2 * 3 * x + x ^^^ 2)" then ()

 else error "rational.sml locate_rule II";

   val SOME r = nex revsets t;

   val (r,(t,asm))::_ = loc revsets t r;

 if term2str t = "(3 - x) * (3 + x) / (3 ^^^ 2 + 2 * 3 * x + x ^^^ 2)" then ()

 else error "rational.sml next_rule II";

   val SOME r = nex revsets t;

   val (r,(t,asm))::_ = loc revsets t r;

 if term2str t = "(3 - x) * (3 + x) / ((3 + x) * (3 + x))" then ()

 else error "rational.sml next_rule III";

   val SOME r = nex revsets t;

   val (r, (t, asm)) :: _ = loc revsets t r;

   val ss = term2str t;

 if ss = "(3 - x) / (3 + x)" andalso terms2str asm = "[\"3 + x ~= 0\"]" then ()

 else error "rational.sml: new behav. in rev-set cancel";

 \--------------------------------------------------------------------------------------/*)

 "-------- 'reverse-ruleset' cancel_p -----------------------------------------";

 "-------- 'reverse-ruleset' cancel_p -----------------------------------------";

 "-------- 'reverse-ruleset' cancel_p -----------------------------------------";

 (*Isabelle2013: the example below shows, why "reverse rewriting" only worked for

   special cases.*)

 (*the term for which reverse rewriting is demonstrated*)

 val t = str2term "(9 + (-1)*x^^^2) / (9 + ((-6)*x + x^^^2))";

 val Rrls {scr=Rfuns {init_state=ini,locate_rule=loc,

 		       next_rule=nex,normal_form=nor,...},...} = cancel_p;

 (*normal_form produces the result in ONE step*)

 val SOME (t',_) = nor t; 

 term2str t' = "(3 + 1 * x) / (3 + -1 * x)";

 (*initialize the interpreter state used by the 'me'*)

 val SOME (t', asm) = cancel_p_ thy t;

 term2str t' = "(3 + x) / (3 + -1 * x)" (*true*);

 terms2str asm = "[\"3 + -1 * x ~= 0\"]" (*true*);

 val (t,_,revsets,_) = ini t;

 (* WN.10.10.02: dieser Fall terminiert nicht 

            (make_polynomial enth"alt zu viele rules)

 WN060823 'init_state' requires rewriting on specified location in the term

 print_depth 99; Rfuns; print_depth 3;

 WN060831 cycling "sym_order_mult_rls_" "sym_mult_assoc"

          as was with make_polynomial before ?!?*)

 val SOME r = nex revsets t;

 eq_Thm (r, Thm ("sym_#power_Float ((3,0), (0,0)) __ ((2,0), (0,0))", 

 		mk_thm thy "9 = 3 ^^^ 2"));

 (*WN060831 *** id_of_thm

            Exception- ERROR raised ...

 val (r,(t,asm))::_ = loc revsets t r;

 term2str t;

   val SOME r = nex revsets t;

   val (r,(t,asm))::_ = loc revsets t r;

   term2str t;

 *)                    

 (*========== inhibit exn WN130824 TODO =======================================================

 "-------- examples: rls norm_Rational ----------------------------------------";

 "-------- examples: rls norm_Rational ----------------------------------------";

 "-------- examples: rls norm_Rational ----------------------------------------";

 val t = str2term "(3*x+5)/18 - x/2  - -(3*x - 2)/9 = 0";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "1 / 18 = 0" then () else error "rational.sml 1";

 val t = str2term "(17*x - 51)/9 - (-(13*x - 3)/6) + 11 - (9*x - 7)/4 = 0";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "(237 + 65 * x) / 36 = 0" then () 

 else error "rational.sml 2";

 val t = str2term "(1/2 + (5*x)/2)^^^2 - ((13*x)/2 - 5/2)^^^2 - (6*x)^^^2 + 29";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "23 + 35 * x + -72 * x ^^^ 2" then ()

 else error "rational.sml 3";

 (*trace_rewrite:=true;*)

 val t = str2term "Not (6*x is_atom)";

 val SOME (t',_) = rewrite_set_ thy false powers_erls t; term2str t';

 "HOL.True";

 val t = str2term "1 < 2";

 val SOME (t',_) = rewrite_set_ thy false powers_erls t; term2str t';

 "HOL.True";

 val t = str2term "(6*x)^^^2";

 val SOME (t',_) = rewrite_ thy dummy_ord powers_erls false 

 			   (num_str @{thm realpow_def_atom}) t;

 if term2str t' = "6 * x * (6 * x) ^^^ (2 + -1)" then ()

 else error "rational.sml powers_erls (6*x)^^^2";

 val t = str2term "-1 * (-2 * (5 / 2 * (13 * x / 2)))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "65 * x / 2" then () else error "rational.sml 4";

 val t = str2term "1 - ((13*x)/2 - 5/2)^^^2";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 (*bef.040209: if term2str t' = "(-21 + (130 * x + -169 * x ^^^ 2)) / 4"then()*)

 if term2str t' = "(-21 + 130 * x + -169 * x ^^^ 2) / 4" then () 

 else error "rational.sml 5";

 (*SRAM Schalk I, p.92 Nr. 609a*)

 val t = str2term "2*(3 - x/5)/3 - 4*(1 - x/3) - x/3 - 2*(x/2 - 1/4)/27 +5/54";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "(-255 + 112 * x) / 135" then () 

 else error "rational.sml 6";

 (*SRAM Schalk I, p.92 Nr. 610c*)

 val t = str2term "((x- 1)/(x+1) + 1) / ((x- 1)/(x+1) - (x+1)/(x- 1)) - 2";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "(-3 + -1 * x) / 2" then () else error "rational.sml 7";

 (*SRAM Schalk I, p.92 Nr. 476a*)

 val t = str2term "(x^^^2/(1 - x^^^2) + 1)/(x/(1 - x) + 1) * (1 + x)";

 (*. a/b : c/d translated to a/b * d/c .*)

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 (*if term2str t' = "1 / 1" then () else error "rational.sml 8";3.6.03*)

 if term2str t' = "1" then () else error "rational.sml 8";

 (*............................vvv---TODO: sollte gehen mit poly_order *)

 (*Schalk I, p.92 Nr. 472a*)

 val t = str2term "((8*x^^^2 - 32*y^^^2)/(2*x + 4*y))/((4*x - 8*y)/(x + y))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "x + y" then () else error "rational.sml p.92 Nr. 472a";

 (*Schalk I, p.70 Nr. 480b; a/b : c/d translated to a/b * d/c*)

 val t = str2term ("((12*x*y/(9*x^^^2 - y^^^2))/" ^

 		 "(1/(3*x - y)^^^2 - 1/(3*x + y)^^^2)) *" ^

 		 "(1/(x - 5*y)^^^2 - 1/(x + 5*y)^^^2)/" ^

 		 "(20*x*y/(x^^^2 - 25*y^^^2))");

 (*... nicht simpl, zerlegt ...*)

 val t = str2term ("((12*x*y/(9*x^^^2 - y^^^2))/" ^

 		 "(1/(3*x - y)^^^2 - 1/(3*x + y)^^^2))");

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 "(-12 * (x * y ^^^ 3) + 108 * (x * (y * x ^^^ 2))) / (12 * (x * y))";

 (*                             ~~~~~~~~~~ poly_order notwendig!*)

 val t = str2term ("(1/(x - 5*y)^^^2 - 1/(x + 5*y)^^^2)/" ^

 		 "(20*x*y/(x^^^2 - 25*y^^^2))");

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "1 / (x ^^^ 2 + -25 * y ^^^ 2)" then ()

 else error "rational.sml norm_Rational 1 / (x ^^^ 2 + -25 * y ^^^ 2)";

 "nonterm.SK6 ----- SK060904-2a non-termination of add_fraction_p_";

 (*WN.2.6.03 from rlang.sml 56a 

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x) = 4 * (a * b) / (a ^^^ 2 + -1 * b ^^^ 2)";

 val NONE = rewrite_set_ thy false common_nominator_p t;

 WN060831 nonterm.SK7 

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x)";

 val NONE = add_fraction_p_ thy t; 

 *)

 (* ------------------------------------------------------------------- *)

 (*---------vvv------------ MG: ab 1.7.03 ----------------vvv-----------*)

 (*                 Simplifier fuer beliebige Buchterme                 *) 

 (* ------------------------------------------------------------------- *)

 (*----------------------- norm_Rational_mg ----------------------------*)

 (* ------------------------------------------------------------------- *)

 "-------- numeral rationals -----------------------------";

 "-------- numeral rationals -----------------------------";

 "-------- numeral rationals -----------------------------";

 (*SRA Schalk I, p.40 Nr. 164b *)

 val t = str2term "(47/6 - 76/9 + 13/4)/(35/12)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = "19 / 21" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 1";

 (*SRA Schalk I, p.40 Nr. 166a *)

 val t = str2term "((5/4)/(4+22/7) + 37/20)*(110/3 - 110/9 * 23/11)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = "45 / 2" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 2";

 "-------- cancellation ----------------------------------";

 "-------- cancellation ----------------------------------";

 "-------- cancellation ----------------------------------";

 (* e190c Stefan K.*)

 val t = str2term

 "((1 + 9 * a ^^^ 2)*(1 + 3 * a))/((3 * a + 9 * a ^^^ 2)*(1 + 3 * a))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(1 + 9 * a ^^^ 2) / (3 * a + 9 * a ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 3";

 (* e192b Stefan K.*)

 val t = str2term

 "((x ^^^ 2)*(7 * x + (-1) * y))/((y ^^^ 2)*(7 * x + (-1) * y))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "x ^^^ 2 / y ^^^ 2"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 4";

 (*SRC Schalk I, p.66 Nr. 379c *)

 val t = str2term 

 "(a - b)/(b - a)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "-1"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 5";

 (*SRC Schalk I, p.66 Nr. 380b *)

 val t = str2term 

 "15*(3*x+3)*(4*x+9)/(12*(2*x+7)*(5*x+5))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(27 + 12 * x) / (28 + 8 * x)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 6";

 (*Schalk I, p.60 Nr. 215c *)

 (* Falsches Ergebnis: rechnet lange und cancel_p kann nicht weiter krzen!!!*)

 (* WN060831????MG1 

 val t = str2term "(a+b)^^^4*(x - y)/((x - y)^^^3*(a+b)^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(a ^^^ 4 * x + -1 * a ^^^ 4 * y + 4 * a ^^^ 3 * b * x + -4 * a ^^^ 3 * b * y + 6 * a ^^^ 2 * b ^^^ 2 * x + -6 * a ^^^ 2 * b ^^^ 2 * y + 4 * a * b ^^^ 3 * x + -4 * a * b ^^^ 3 * y + b ^^^ 4 * x + -1 * b ^^^ 4 * y) /(a ^^^ 2 * x ^^^ 3 + -3 * a ^^^ 2 * x ^^^ 2 * y + 3 * a ^^^ 2 * x * y ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 3 + 2 * a * b * x ^^^ 3 + -6 * a * b * x ^^^ 2 * y + 6 * a * b * x * y ^^^ 2 + -2 * a * b * y ^^^ 3 + b ^^^ 2 * x ^^^ 3 + -3 * b ^^^ 2 * x ^^^ 2 * y + 3 * b ^^^ 2 * x * y ^^^ 2 + -1 * b ^^^ 2 * y ^^^ 3)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 7";

 *)

 (*val t = str2term 

 "(a ^^^ 4 * x + -1 * a ^^^ 4 * y + 4 * a ^^^ 3 * b * x + -4 * a ^^^ 3 * b * y + 6 * a ^^^ 2 * b ^^^ 2 * x + -6 * a ^^^ 2 * b ^^^ 2 * y + 4 * a * b ^^^ 3 * x + -4 * a * b ^^^ 3 * y + b ^^^ 4 * x + -1 * b ^^^ 4 * y) /(a ^^^ 2 * x ^^^ 3 + -3 * a ^^^ 2 * x ^^^ 2 * y + 3 * a ^^^ 2 * x * y ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 3 + 2 * a * b * x ^^^ 3 + -6 * a * b * x ^^^ 2 * y + 6 * a * b * x * y ^^^ 2 + -2 * a * b * y ^^^ 3 + b ^^^ 2 * x ^^^ 3 + -3 * b ^^^ 2 * x ^^^ 2 * y + 3 * b ^^^ 2 * x * y ^^^ 2 + -1 * b ^^^ 2 * y ^^^ 3)"

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;*)

 (* uncaught exception nonexhaustive binding failure

    raised at: stdIn:93.1-93.51 *)

 (*Schalk I, p.66 Nr. 381a *)

 (* ACHTUNG: rechnet ca. 2 Minuten !!! *)

 (* WN060831???MG2

 val t = str2term "18*(a+b)^^^3*(a - b)^^^2/(72*(a - b)^^^3*(a+b)^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(a + b) / (4 * a + -4 * b)"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 8";

 *)

 (*SRC Schalk I, p.66 Nr. 381b *)

 val t = str2term 

 "(4*x^^^2 - 20*x + 25)/(2*x - 5)^^^3";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "-1 / (5 + -2 * x)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 9";

 (*SRC Schalk I, p.66 Nr. 381c *)

 val t = str2term 

 "(27*a^^^3+9*a^^^2+3*a+1)/(27*a^^^3+18*a^^^2+3*a)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(1 + 9 * a ^^^ 2) / (3 * a + 9 * a ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 10";

 (*SRC Schalk I, p.66 Nr. 383a *)

 val t = str2term 

 "(5*a^^^2 - 5*a*b)/(a - b)^^^2";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "5 * a / (a + -1 * b)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 11";

 "-------- common denominator ----------------------------";

 "-------- common denominator ----------------------------";

 "-------- common denominator ----------------------------";

 (*SRA Schalk I, p.67 Nr. 403a *)

 val t = str2term 

 "4/x - 3/y - 1";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(-3 * x + 4 * y + -1 * x * y) / (x * y)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 12";

 (*SRA Schalk I, p.67 Nr. 407b *)

 val t = str2term 

 "(2*a+3*b)/(b*c) + (3*c+a)/(a*c) - (2*a^^^2+3*b*c)/(a*b*c)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "4 / c"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 13";

 (*SRA Schalk I, p.67 Nr. 410b *)

 val t = str2term 

 "1/(x+1) + 1/(x+2) - 2/(x+3)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(5 + 3 * x) / (6 + 11 * x + 6 * x ^^^ 2 + x ^^^ 3)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 14";

 (*SRA Schalk I, p.67 Nr. 413b *)

 val t = str2term 

 "(1+x)/(1 - x) - (1 - x)/(1+x) + 2*x/(1 - x^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "6 * x / (1 + -1 * x ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 15";

 (*SRA Schalk I, p.68 Nr. 414a *)

 val t = str2term 

 "(x + 2)/(x - 1) + (x - 3)/(x - 2) - (x + 1)/((x - 1)*(x - 2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(-2 + -5 * x + 2 * x ^^^ 2) / (2 + -3 * x + x ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 16";

 (*SRA Schalk I, p.68 Nr. 423a *)

 val t = str2term 

 "(2*x+3*y)/x + (4*x^^^3 - x*y^^^2 - 3*y^^^3)/(x^^^3 - 2*x^^^2*y+x*y^^^2) - (5*x+6*y)/(x - y)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "1"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 17";

 (*SRA Schalk I, p.68 Nr. 428b *)

 val t = str2term 

 "1/(a - b)^^^2 + 1/(a+b)^^^2 - 2/(a^^^2 - b^^^2) - 4*(b^^^2 - 1)/(a^^^2 - b^^^2)^^^2";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "4 / (a ^^^ 4 + -2 * a ^^^ 2 * b ^^^ 2 + b ^^^ 4)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 18";

 (*SRA Schalk I, p.68 Nr. 430b *)

 val t = str2term 

 "a^^^2/(a - 3*b) - 108*a*b^^^3/((a+3*b)*(a^^^2 - 9*b^^^2)) - 9*b^^^2*(a - 3*b)/(a+3*b)^^^2";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "a + 3 * b"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 19";

 (*SRA Schalk I, p.68 Nr. 432 *)

 val t = str2term 

 "(a^^^2+a*b)/(a^^^2 - b^^^2) - (b^^^2 - a*b)/(b^^^2 - a^^^2) + a^^^2*(a - b)/(a^^^3 - a^^^2*b) - 2*a*(a^^^2 - b^^^2)/(a^^^3 - a*b^^^2) - 2*b^^^2/(a^^^2 - b^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "0"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 20";

 (*Eigenes*)

 val t = str2term 

 "3*a/(a*b) + x/y";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(3 * y + b * x) / (b * y)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 21";

 "-------- multiply and cancel ---------------------------";

 "-------- multiply and cancel ---------------------------";

 "-------- multiply and cancel ---------------------------";

 (*SRM Schalk I, p.68 Nr. 436a *)

 val t = str2term 

 "3*(x+y)/(15*(x - y)) * 25*(x - y)^^^2/(18*(x+y)^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(5 * x + -5 * y) / (18 * x + 18 * y)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 22";

 (*SRM.test Schalk I, p.68 Nr. 436b *)

 (*WN060420???MG3 crashes with method 'simplify' in 

   IsacCore > Simplification > Rational Terms > Multiplication > No.2*)

 val t = str2term "5*a*(a - b)^^^2*(a + b)^^^3/(7*b*(a - b)^^^3) * 7*b/(a + b)^^^3";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "5 * a / (a + -1 * b)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 23";

 (*Schalk I, p.68 Nr. 437a *)

 val t = str2term "(3*a - 4*b)/(4*c+3*e) * (3*a+4*b)/(9*a^^^2 - 16*b^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if (term2str t) = "1 / (4 * c + 3 * e)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 24";

 "----- S.K. corrected non-termination 060904";

 val t = str2term "(3*a - 4*b) * (3*a+4*b)/((4*c+3*e)*(9*a^^^2 - 16*b^^^2))";

 val SOME (t',_) = rewrite_set_ thy false make_polynomial t;

 term2str t';

 if term2str t' = 

   "(9 * a ^^^ 2 + -16 * b ^^^ 2) /\n(36 * a ^^^ 2 * c + 27 * a ^^^ 2 * e + -64 * b ^^^ 2 * c +\n -48 * b ^^^ 2 * e)"

 (*"(9 * a ^^^ 2 + -16 * b ^^^ 2) / (36 * a ^^^ 2 * c + 27 * a ^^^ 2 * e + -64 * b ^^^ 2 * c + -48 * b ^^^ 2 * e)"*)

 then () else error "rational.sml: S.K.8..corrected 060904-6";

 "----- S.K. corrected non-termination of cancel_p_";

 val t'' = str2term ("(9 * a ^^^ 2 + -16 * b ^^^ 2) /" ^

 "(36 * a^^^2 * c + (27 * a^^^2 * e + (-64 * b^^^2 * c + -48 * b^^^2 * e)))");

 val SOME (t',_) = rewrite_set_ thy false cancel_p t'';

 if term2str t' = "1 / (4 * c + 3 * e)" then ()

 else error "rational.sml: diff.behav. in cancel_p S.K.8";

 (*Schalk I, p.68 Nr. 437b *)

 (* nonterm.SK9 loops: cancel_p kann nicht weiter kuerzen!!! *)

 val t'' = str2term "(a + b)/(x^^^2 - y^^^2) * ((x - y)^^^2/(a^^^2 - b^^^2))";

 (* val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t'';

    *)

 "================delete===";

 (*a casual output from above*)

 val t = str2term 

 "(a * x ^^^ 2 + -2 * a * x * y + a * y ^^^ 2 + b * x ^^^ 2 + -2 * b * x * y + b * y ^^^ 2) /(a ^^^ 2 * x ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 2 + -1 * b ^^^ 2 * x ^^^ 2 + b ^^^ 2 * y ^^^ 2)"; 

 (* WN060831 nonterm.SK10 

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 *)

 (*SRM Schalk I, p.68 Nr. 438a *)

 val t = str2term 

 "x*y/(x*y - y^^^2)*(x^^^2 - x*y)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "x ^^^ 2"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 24";

 (*SRM Schalk I, p.68 Nr. 439b *)

 val t = str2term 

 "(4*x^^^2+4*x+1)*((x^^^2 - 2*x^^^3)/(4*x^^^2+2*x))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(x + -4 * x ^^^ 3) / 2"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 25";

 (*SRM Schalk I, p.68 Nr. 440a *)

 val t = str2term 

 "(x^^^2 - 2*x)/(x^^^2 - 3*x) * (x - 3)^^^2/(x^^^2 - 4)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(-3 + x) / (2 + x)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 26";

 "----- Schalk I, p.68 Nr. 440b SK11 works since 0707xx";

 val t = str2term 

 "(a^^^3 - 9*a)/(a^^^3*b - a*b^^^3)*(a^^^2*b+a*b^^^2)/(a+3)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "(-3 * a + a ^^^ 2) / (a + -1 * b)" then ()

 else error "rational.sml: diff.behav. in norm_Rational 27";

 "----- SK12 works since 0707xx";

 val t = str2term "(a^^^3 - 9*a)*(a^^^2*b+a*b^^^2)/((a^^^3*b - a*b^^^3)*(a+3))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; term2str t';

 if term2str t' = "(-3 * a + a ^^^ 2) / (a + -1 * b)" then ()

 else error "rational.sml: diff.behav. in norm_Rational 28";

 "-------- common denominator and multiplication ---------";

 "-------- common denominator and multiplication ---------";

 "-------- common denominator and multiplication ---------";

 (*SRAM Schalk I, p.69 Nr. 441b *)

 val t = str2term "(4*a/3 + 3*b^^^2/a^^^3 + b/(4*a))*(4*b/(3*a))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

   "(36 * b ^^^ 3 + 3 * a ^^^ 2 * b ^^^ 2 + 16 * a ^^^ 4 * b) / (9 * a ^^^ 4)"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 28";

 (*SRAM Schalk I, p.69 Nr. 442b *)

 val t = str2term "(15*a^^^2/x^^^3 - 5*b^^^4/x^^^2 + 25*c^^^2/x)*(x^^^3/(5*a*b^^^3*c^^^3)) + 1/c^^^3 * (b*x/a - 3*a/b^^^3)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "5 * x ^^^ 2 / (a * b ^^^ 3 * c)"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 29";

 (*SRAM Schalk I, p.69 Nr. 443b *)

 val t = str2term "(a/2 + b/3)*(b/3 - a/2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(-9 * a ^^^ 2 + 4 * b ^^^ 2) / 36"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 30";

 (*SRAM Schalk I, p.69 Nr. 445b *)

 val t = str2term "(a^^^2/9 + 2*a/(3*b) + 4/b^^^2)*(a/3 - 2/b) + 8/b^^^3";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "a ^^^ 3 / 27"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 31";

 (*SRAM Schalk I, p.69 Nr. 446b *)

 val t = str2term "(x/(5*x + 4*y) - y/(5*x - 4*y) + 1)*(25*x^^^2 - 16*y^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "30 * x ^^^ 2 + -9 * x * y + -20 * y ^^^ 2"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 32";

 (*SRAM Schalk I, p.69 Nr. 449a *)(*Achtung: rechnet ca 8 Sekunden*)

 val t = str2term 

 "(2*x^^^2/(3*y)+x/y^^^2)*(4*x^^^4/(9*y^^^2)+x^^^2/y^^^4)*(2*x^^^2/(3*y) - x/y^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = "(-81 * x ^^^ 4 + 16 * x ^^^ 8 * y ^^^ 4) / (81 * y ^^^ 8)"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 33";

 (*SRAM Schalk I, p.69 Nr. 450a *)

 val t = str2term 

 "(4*x/(3*y)+2*y/(3*x))^^^2 - (2*y/(3*x) - 2*x/y)*(2*y/(3*x)+2*x/y)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "(52 * x ^^^ 2 + 16 * y ^^^ 2) / (9 * y ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 34";

 "-------- double fractions ------------------------------";

 "-------- double fractions ------------------------------";

 "-------- double fractions ------------------------------";

 (*SRD Schalk I, p.69 Nr. 454b *)

 val t = str2term 

 "((2 - x)/(2*a)) / (2*a/(x - 2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(-4 + 4 * x + -1 * x ^^^ 2) / (4 * a ^^^ 2)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 35";

 (*SRD Schalk I, p.69 Nr. 455a *)

 val t = str2term 

 "(a^^^2 + 1)/(a^^^2 - 1) / ((a+1)/(a - 1))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(1 + a ^^^ 2) / (1 + 2 * a + a ^^^ 2)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 36";

 "----- Schalk I, p.69 Nr. 455b";

 val t = str2term "(x^^^2 - 4)/(y^^^2 - 9)/((2+x)/(3 - y))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if term2str t = "(2 + -1 * x) / (3 + y)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 37";

 "----- SK060904-1a non-termination of cancel_p_ ?: worked before 0707xx";

 val t = str2term "(x^^^2 - 4)*(3 - y)/((y^^^2 - 9)*(2+x))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "(2 + -1 * x) / (3 + y)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 37b";

 "----- ?: worked before 0707xx";

 val t = str2term "(3 + -1 * y) / (-9 + y ^^^ 2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "-1 / (3 + y)" then ()

 else error "rational.sml: -1 / (3 + y) norm_Rational";

 (*SRD Schalk I, p.69 Nr. 456b *)

 val t = str2term 

 "(b^^^3 - b^^^2)/(b^^^2+b)/(b^^^2 - 1)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = "b / (1 + 2 * b + b ^^^ 2)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 38";

 (*SRD Schalk I, p.69 Nr. 457b *)

 val t = str2term 

 "(16*a^^^2 - 9*b^^^2)/(2*a+3*a*b) / ((4*a+3*b)/(4*a^^^2 - 9*a^^^2*b^^^2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

   "8 * a ^^^ 2 + -6 * a * b + -12 * a ^^^ 2 * b + 9 * a * b ^^^ 2"

 then () else error "rational.sml: diff.behav. in norm_Rational_mg 39";

 "----- Schalk I, p.69 Nr. 458b works since 0707";

 val t = str2term 

 "(2*a^^^2*x - a^^^2)/(a*x - b*x) / (b^^^2*(2*x - 1)/(x*(a - b)))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "a ^^^ 2 / b ^^^ 2" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 39b";

 (*SRD Schalk I, p.69 Nr. 459b *)

 val t = str2term "(a^^^2 - b^^^2)/(a*b) / (4*(a+b)^^^2/a)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "(a + -1 * b) / (4 * a * b + 4 * b ^^^ 2)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 41";

 (*Schalk I, p.69 Nr. 460b nonterm.SK

 val t = str2term 

 "(9*(x^^^2 - 8*x+16)/(4*(y^^^2 - 2*y+1)))/((3*x - 12)/(16*y - 16))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if term2str t = 

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 42";

 val t = str2term 

 "9*(x^^^2 - 8*x+16)*(16*y - 16)/(4*(y^^^2 - 2*y+1)*(3*x - 12))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t;

 ... non terminating.

 val SOME (t',_) = rewrite_set_ thy false make_polynomial t;

 "(-2304 + 1152 * x + 2304 * y + -144 * x ^^^ 2 + -1152 * x * y + 144 * x ^^^ 2 * y) /(-48 + 12 * x + 96 * y + -24 * x * y + -48 * y ^^^ 2 + 12 * x * y ^^^ 2)";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t';

 ... non terminating.*)

 (*SRD Schalk I, p.70 Nr. 472a *)

 val t = str2term ("((8*x^^^2 - 32*y^^^2)/(2*x + 4*y))/" ^

 		 "((4*x - 8*y)/(x + y))");

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "x + y"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 43";

 (*----------------------------------------------------------------------*)

 (*---------------------- Einfache Dppelbrche --------------------------*)

 (*----------------------------------------------------------------------*)

 (*SRD Schalk I, p.69 Nr. 461a *)

 val t = str2term 

 "(2/(x+3) + 2/(x - 3)) / (8*x/(x^^^2 - 9))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "1 / 2"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 44";

 (*SRD Schalk I, p.69 Nr. 464b *)

 val t = str2term 

 "(a - a/(a - 2)) / (a + a/(a - 2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(3 + -1 * a) / (1 + -1 * a)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 45";

 (*SRD Schalk I, p.69 Nr. 465b *)

 val t = str2term 

 "((x+3*y)/9 + (4*y^^^2 - 9*z^^^2)/(16*x)) /(x/9+y/6+z/4)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(4 * x + 6 * y + -9 * z) / (4 * x)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 46";

 (*SRD Schalk I, p.69 Nr. 466b *)

 val t = str2term 

 "((1 - 7*(x - 2)/(x^^^2 - 4)) / (6/(x+2))) / (3/(x+5)+30/(x^^^2 - 25))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "(25 + -10 * x + x ^^^ 2) / 18"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 47";

 (*SRD Schalk I, p.70 Nr. 469 *)

 val t = str2term 

 "3*b^^^2/(4*a^^^2 - 8*a*b + 4*b^^^2)/(a/(a^^^2*b - b^^^3) + (a - b)/(4*a*b^^^2+4*b^^^3) - 1/(4*b^^^2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 "3 * b ^^^ 3 / (2 * a + -2 * b)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 48";

 (*----------------------------------------------------------------------*)

 (*---------------------- Mehrfache Dppelbrueche ------------------------*)

 (*----------------------------------------------------------------------*)

 (*SRD.test Schalk I, p.70 Nr. 476b *) (* Rechenzeit: 10 sec *)

 (*WN060419 crashes with method 'simplify' ????SK*)

 val t = str2term 

 "((a^^^2 - b^^^2)/(2*a*b)+2*a*b/(a^^^2 - b^^^2))/((a^^^2+b^^^2)/(2*a*b)+1) / ((a^^^2+b^^^2)^^^2/(a+b)^^^2)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 if term2str t = "1 / (a ^^^ 2 + -1 * b ^^^ 2)" then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 49";

 "----- Schalk I, p.70 Nr. 477a";

 (* MG Achtung: terme explodieren; Bsp zu komplex; 

    L???ung sollte (ziemlich grosser) Faktorisierter Ausdruck sein 

 val t = str2term "b*y/(b - 2*y)/((b^^^2 - y^^^2)/(b+2*y)) /" ^

 		 "(b^^^2*y+b*y^^^2)*(a+x)^^^2/((b^^^2 - 4*y^^^2)*(a+2*x)^^^2)";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t;

 val t = str2term "b*y*(b+2*y)*(b^^^2 - 4*y^^^2)*(a+2*x)^^^2 / " ^

 		 "((b - 2*y)*(b^^^2 - y^^^2)*(b^^^2*y+b*y^^^2)*(a+x)^^^2)";

 val SOME (t,_) = rewrite_set_ thy false make_polynomial t;

 ????SK ???MG*)

 "----- Schalk I, p.70 Nr. 478b ----- Rechenzeit: 5 sec";

 val t = str2term ("(a - (a*b+b^^^2)/(a+b))/(b+(a - b)/(1+(a+b)/(a - b))) / " ^

 		 "((a - a^^^2/(a+b))/(a+(a*b)/(a - b)))");

 val SOME (t',_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if term2str t' = 

 "(2 * a ^^^ 3 + 2 * a ^^^ 2 * b) / (a ^^^ 2 * b + b ^^^ 3)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 51";

 (* TODO.new_c:WN050820 STOP_REW_SUB introduced gave ...

 if term2str t' = "(a ^^^ 4 + -1 * a ^^^ 2 * b ^^^ 2) /(a * b * (b + (a * (a + -1 * b) + -1 * b * (a + -1 * b)) / (2 * a)) * (a + -1 * b))" then ()

 else error "rational.sml: works again";

 re-outcommented with TODO.new_c: cvs before 071227, 11:50*)

 (*Schalk I, p.70 Nr. 480a *)

 (* Achtung: rechnet ewig; cancel_p kann nicht krzen: WN060831 nonterm.SK00

 val t = str2term 

 "(1/x+1/y+1/z)/(1/x - 1/y - 1/z) / (2*x^^^2/(x^^^2 - z^^^2)/(x/(x+z)+x/(x - z)))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) = 

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 52";

 (*MG Berechne Zwischenergebnisse: WN060831 nonterm.SK00*)

 val t = str2term 

 "(1/x+1/y+1/z)/(1/x - 1/y - 1/z)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 "(x ^^^ 2 * y ^^^ 2 * z + x ^^^ 2 * y * z ^^^ 2 + x * y ^^^ 2 * z ^^^ 2) /

 (-1 * x ^^^ 2 * y ^^^ 2 * z + -1 * x ^^^ 2 * y * z ^^^ 2 + x * y ^^^ 2 * z ^^^ 2)";

 val t = str2term 

 "2*x^^^2/(x^^^2 - z^^^2)/(x/(x+z)+x/(x - z))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 "1"

 (* SK 1. Ausdruck kann nicht weiter gekrzt werden; cancel_p !!!*)

 ###  rls: cancel_p on: 

 (x ^^^ 2 * (y ^^^ 2 * z) + x ^^^ 2 * (y * z ^^^ 2) + x * (y ^^^ 2 * z ^^^ 2)) /

 (-1 * (x ^^^ 2 * (y ^^^ 2 * z)) + -1 * (x ^^^ 2 * (y * z ^^^ 2)) + x * (y ^^^ 2 * z ^^^ 2))

 GC #3.61.81.101.197.17503:   (0 ms)

 *** RATIONALS_DIRECT_CANCEL_EXCEPTION: Invalid fraction

 val t = str2term 

 "(x^^^2 * (y^^^2 * z) + x^^^2 * (y * z^^^2) + x * (y^^^2 * z^^^2)) / (-1 * (x^^^2 * (y^^^2 * z)) + -1 * (x^^^2 * (y * z^^^2)) + x * (y^^^2 * z^^^2))";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 (*uncaught exception nonexhaustive binding failure*)

 (* Das kann er aber krzen !!????: *)

 val t = str2term 

 "(x^^^2 * (y^^^2 * z) +  x * (y^^^2 * z^^^2)) / (-1 * (x^^^2 * (y * z^^^2)) + x * (y^^^2 * z^^^2))";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 "(-1 * (y * x) + -1 * (z * y)) / (1 * (z * x) + -1 * (z * y))";

 *)

 "-------- crucial examples ------------------------------";

 "-------- crucial examples ------------------------------";

 "-------- crucial examples ------------------------------";

 (*Schalk I, p.60 Nr. 215d *)

 (* Achtung: rechnet ewig ...

 val t = str2term "(a-b)^^^3 * (x+y)^^^4 / ((x+y)^^^2 * (a-b)^^^5)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t; noterm.SK

 *)

 (* Kein Wunder, denn Z???ler und Nenner extra als Polynom dargestellt ergibt:*)

 (*

 val t = str2term "(a-b)^^^3 * (x+y)^^^4";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 "a^^^3 * x^^^4 + 4 * a^^^3 * x^^^3 * y +6 * a^^^3 * x^^^2 * y^^^2 +4 * a^^^3 * x * y^^^3 +a^^^3 * y^^^4 +-3 * a^^^2 * b * x^^^4 +-12 * a^^^2 * b * x^^^3 * y +-18 * a^^^2 * b * x^^^2 * y^^^2 +-12 * a^^^2 * b * x * y^^^3 +-3 * a^^^2 * b * y^^^4 +3 * a * b^^^2 * x^^^4 +12 * a * b^^^2 * x^^^3 * y +18 * a * b^^^2 * x^^^2 * y^^^2 +12 * a * b^^^2 * x * y^^^3 +3 * a * b^^^2 * y^^^4 +-1 * b^^^3 * x^^^4 +-4 * b^^^3 * x^^^3 * y +-6 * b^^^3 * x^^^2 * y^^^2 +-4 * b^^^3 * x * y^^^3 +-1 * b^^^3 * y^^^4";

 val t = str2term "((x+y)^^^2 * (a-b)^^^5)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 "a^^^5 * x^^^2 + 2 * a^^^5 * x * y + a^^^5 * y^^^2 +-5 * a^^^4 * b * x^^^2 +-10 * a^^^4 * b * x * y +-5 * a^^^4 * b * y^^^2 +10 * a^^^3 * b^^^2 * x^^^2 +20 * a^^^3 * b^^^2 * x * y +10 * a^^^3 * b^^^2 * y^^^2 +-10 * a^^^2 * b^^^3 * x^^^2 +-20 * a^^^2 * b^^^3 * x * y +-10 * a^^^2 * b^^^3 * y^^^2 +5 * a * b^^^4 * x^^^2 +10 * a * b^^^4 * x * y +5 * a * b^^^4 * y^^^2 +-1 * b^^^5 * x^^^2 +-2 * b^^^5 * x * y +-1 * b^^^5 * y^^^2";

 *)

 (*anscheinend macht dem Rechner das Krzen diese Bruches keinen Spass mehr ...*)

 (*--------------------------------------------------------------------*)

 (*Schalk I, p.70 Nr. 480b 

 val t = str2term "((12*x*y/(9*x^^^2 - y^^^2))/" ^

 		 "(1/(3*x - y)^^^2 - 1/(3*x + y)^^^2)) *" ^

 		 "(1/(x - 5*y)^^^2 - 1/(x + 5*y)^^^2)/" ^

 		 "(20*x*y/(x^^^2 - 25*y^^^2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 SK.nonterm

 Kann nicht weiter vereinfacht werden !!!!?? *)

 (*--------------------------------------------------------------------*)

 "---- MGs test set";

 val t = str2term " (1 + x^^^5) / (y + x) + x^^^3 / x ";

 val SOME (t,_) = rewrite_set_ thy false common_nominator_p t;

 if term2str t = "(1 + x ^^^ 3 + x ^^^ 5 + y * x ^^^ 2) / (x + y)" then()

 else error "";

 (*--------------------------------------------------------------------*)

 (* cancel_p liefert nicht immer Polynomnormalform (2): WN060831???SK3b

    ---> Sortierung FALSCH !!  *)

 val t = str2term "b^^^3 * a^^^5/a ";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 "1 * (a^^^4 * b^^^3) / 1"; (*OK*)

 val t = str2term "b^^^3 * a^^^5/b ";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 "1 * (b^^^2 * a^^^5) / 1"; (*cancel_p sortiert hier falsch um!*)

 (* Problem liegt NICHT bei ord_make_polynomial! (siehe folgende Bsple) *)

 (*

 val x = str2term "x"; val bdv = str2term "bdv";

 val t1 = str2term "b^^^2 * a^^^5";

 val t2 = str2term "a^^^5 * b^^^2 ";

 ord_make_polynomial false Rational.thy [(x,bdv)] (t1,t2); (*false*)

 *)

 (* ==> "b^^^2 * a^^^5" > "a^^^5 * b^^^2 " ... OK!*)

 (*--------------------------------------------------------------------*)

 (* cancel_p liefert nicht immer Polynomnormalform (2): WN060831???SK3c

    ---> erzeugt berflssige "1 * ..."

 val t = str2term "-1 / (3 + y)";

 (*~~         *)

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 "-1 / (3 + 1 * y)";

 (********* Das ist das PROBLEM !!!!!!!??? *******************)

 (* -1 im Z???ler der Angabe verursacht das Problem !*)

 *)

 (* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *)

 "----- MGs test set";

 val t = str2term "(a^^^2 + -1)/(a+1)";

 val SOME (t',_) = rewrite_set_ thy false cancel_p t;

 if term2str t' = "(-1 + a) / 1" then ()

 else error "rational.sml MG tests 3d";

 "----- NOT TERMINATING ?: worked before 0707xx";

 val t = str2term "(a^^^2 - 1)*(b + 1) / ((b^^^2 - 1)*(a+1))";

 val SOME (t'',_) = rewrite_set_ thy false norm_Rational t;

 if term2str t'' = "(1 + -1 * a) / (1 + -1 * b)" then ()

 else error "rational.sml MG tests 3e";

 "----- corrected SK060905";

 val t = str2term "(4*x^^^2 - 20*x + 25)/(2*x - 5)^^^3";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if term2str t' = "-1 / (5 + -2 * x)" then ()

 else error "rational.sml corrected SK060905";

 "-------- examples for Stefan Karnels thesis ------------";

 "-------- examples for Stefan Karnels thesis ------------";

 "-------- examples for Stefan Karnels thesis ------------";

 (*SRAM Schalk I, p.69 Nr. 442b --- abgewandelt*)

 val t = str2term 

 "(15*a^^^4/(a*x^^^3) - 5*a*((b^^^4 - 5*c^^^2*x)/x^^^2))*(x^^^3/(5*a*b^^^3*c^^^3)) + a/c^^^3 * (x*(b/a) - 3*b*(a/b^^^4))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 term2str t;

 if (term2str t) =

 "5 * x ^^^ 2 / (b ^^^ 3 * c)"

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 53";

 "-------- me Schalk I No.186 ----------------------------";

 "-------- me Schalk I No.186 ----------------------------";

 "-------- me Schalk I No.186 ----------------------------";

 val fmz = ["Term ((14 * x * y) / ( x * y ))",

 	   "normalform N"];

 val (dI',pI',mI') =

   ("Rational",["rational","simplification"],

    ["simplification","of_rationals"]);

 val p = e_pos'; val c = []; 

 val (p,_,f,nxt,_,pt) = CalcTreeTEST [(fmz, (dI',pI',mI'))];

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt;

 val (p,_,f,nxt,_,pt) = me nxt p c pt; f2str f;

 val (p,_,f,nxt,_,pt) = me nxt p c pt; f2str f;

 val (p,_,f,nxt,_,pt) = me nxt p c pt; f2str f;(*++ for explicit script*)

 val (p,_,f,nxt,_,pt) = me nxt p c pt; f2str f;(*++ for explicit script*)

 case (f2str f, nxt) of

     ("14", ("End_Proof'", _)) => ()

   | _ => error "rational.sml diff.behav. in me Schalk I No.186";

 "-------- interSteps ..Simp_Rat_Double_No-1.xml ---------";

 "-------- interSteps ..Simp_Rat_Double_No-1.xml ---------";

 "-------- interSteps ..Simp_Rat_Double_No-1.xml ---------";

 states:=[];

 CalcTree

 [(["Term (((2 - x)/(2*a)) / (2*a/(x - 2)))", "normalform N"], 

   ("Rational",["rational","simplification"],

   ["simplification","of_rationals"]))];

 Iterator 1;

 moveActiveRoot 1;

 autoCalculate 1 CompleteCalc;

 val ((pt,p),_) = get_calc 1; show_pt pt;

 interSteps 1 ([1],Res);

 val ((pt,p),_) = get_calc 1; show_pt pt;

 "-------- interSteps ..Simp_Rat_Cancel_No-1.xml ---------";

 "-------- interSteps ..Simp_Rat_Cancel_No-1.xml ---------";

 "-------- interSteps ..Simp_Rat_Cancel_No-1.xml ---------";

 states:=[];

 CalcTree

 [(["Term ((a^2 + -1*b^2) / (a^2 + -2*a*b + b^2))", "normalform N"], 

   ("Rational",["rational","simplification"],

   ["simplification","of_rationals"]))];

 Iterator 1;

 moveActiveRoot 1;

 autoCalculate 1 CompleteCalc;

 val ((pt,p),_) = get_calc 1; show_pt pt;

 (*========== inhibit exn 110314 ================================================

 (*with explicit script done already... and removed [1,..] at below...

 interSteps 1 ([1],Res);

 val ((pt,p),_) = get_calc 1; show_pt pt;

 *)

 interSteps 1 ([2],Res);

 val ((pt,p),_) = get_calc 1; show_pt pt;

 interSteps 1 ([2,1],Res);

 val ((pt,p),_) = get_calc 1; show_pt pt;

 val newnds = children (get_nd pt [2,1]) (*see "fun detailrls"*);

 (*if length newnds = 12 then () WN060905*)

 if length newnds = 13 then ()

 else error "rational.sml: interSteps cancel_p rev_rew_p";

 val p = ([2,1,9],Res);

 getTactic 1 p;

 val (_, tac, _) = pt_extract (pt, p);

 (*case tac of SOME (Rewrite ("sym_real_plus_binom_times1", _)) => ()

 WN060905*)

 case tac of SOME (Rewrite ("sym_real_add_mult_distrib2", _)) => ()

 | _ => error "rational.sml: getTactic, sym_real_plus_binom_times1";

 ============ inhibit exn 110314 ==============================================*)

 "-------- investigate rulesets for cancel_p -------------";

 "-------- investigate rulesets for cancel_p -------------";

 "-------- investigate rulesets for cancel_p -------------";

 val thy = @{theory "Rational"};

 "---------------- (a^^^2 + -1*b^^^2) / (a^^^2 + -2*a*b + b^^^2)";

 val t = str2term "(a^^^2 + -1*b^^^2) / (a^^^2 + -2*a*b + b^^^2)";

 val tt = str2term "(1 * a + 1 * b) * (1 * a + -1 * b)"(*numerator only*);

 "----- with rewrite_set_";

 val SOME (tt',asm) = rewrite_set_ thy false make_polynomial tt;

 term2str tt'= "a ^^^ 2 + -1 * b ^^^ 2" (*true*);

 val tt = str2term "((1 * a + -1 * b) * (1 * a + -1 * b))"(*denominator only*);

 val SOME (tt',asm) = rewrite_set_ thy false make_polynomial tt;

 term2str tt' = "a ^^^ 2 + -2 * a * b + b ^^^ 2" (*true*);

 "----- with make_deriv";

 val SOME (tt, _) = factout_p_ thy t; term2str tt =

 "(1 * a + 1 * b) * (1 * a + -1 * b) / ((1 * a + -1 * b) * (1 * a + -1 * b))";

 (*

 "--- with ruleset as before 060829";

 val {rules, rew_ord=(_,ro),...} =

     rep_rls (assoc_rls "make_polynomial");

 val der = make_deriv thy Atools_erls rules ro NONE tt;

 print_depth 99; map (term2str o #1) der; print_depth 3;

 print_depth 99; map (rule2str o #2) der; print_depth 3;

 ... did not terminate*)

 "--- with simpler ruleset";

 val {rules, rew_ord=(_,ro),...} =

     rep_rls (assoc_rls "rev_rew_p");

 val der = make_deriv thy Atools_erls rules ro NONE tt;

 print_depth 99; writeln (deriv2str der); print_depth 3;

 print_depth 99; map (term2str o #1) der; print_depth 3;

 "...,(-1 * b ^^^ 2 + a ^^^ 2) / (-2 * (a * b) + a ^^^ 2 + (-1 * b) ^^^ 2) ]";

 print_depth 99; map (rule2str o #2) der; print_depth 3;

 print_depth 99; map (term2str o #1 o #3) der; print_depth 3;

 val der = make_deriv thy Atools_erls rules ro NONE 

 		     (str2term "(1 * a + 1 * b) * (1 * a + -1 * b)");

 print_depth 99; writeln (deriv2str der); print_depth 3;

 val {rules, rew_ord=(_,ro),...} =

     rep_rls (assoc_rls "rev_rew_p");

 val der = make_deriv thy Atools_erls rules ro NONE 

 		     (str2term "(1 * a + -1 * b) * (1 * a + -1 * b)");

 print_depth 99; writeln (deriv2str der); print_depth 3;

 print_depth 99; map (term2str o #1) der; print_depth 3;

 (*WN060829 ...postponed*)

 "-------- investigate format of factout_ and factout_p_ -";

 "-------- investigate format of factout_ and factout_p_ -";

 "-------- investigate format of factout_ and factout_p_ -";

 val {rules, rew_ord = (_,ro),...} = rep_rls (assoc_rls "make_polynomial");

 val (thy, eval_rls) = (@{theory "Rational"}, Atools_erls)(*see 'fun init_state'*);

 val Rrls {scr = Rfuns {init_state,...},...} = assoc_rls "cancel_p";

 "----- see Rational.ML, local cancel_p, fun init_state";

 val t = str2term "(a^^^2 + (-1)*b^^^2) / (a^^^2 + (-2)*a*b + b^^^2)";

 val SOME (t',_) = factout_p_ thy t; term2str t';

 (*

 val rtas = reverse_deriv thy eval_rls rules ro NONE t';

 writeln(trtas2str rst);

 *)

 "----- see Rational.ML, local cancel_p, fun init_state";

 val t = str2term "a^^^2 / a";

 val SOME (t',_) = factout_p_ thy t; 

 term2str t' = "a * a / (1 * a)" (*true*); 

 (*... can be canceled with

 real_mult_div_cancel2 ?k ~= 0 ==> ?m * ?k / (?n * ?k) = ?m / ?n"*)

 (* sml/ME/rewtools.sml:

 val rtas = reverse_deriv thy Atools_erls rules ro NONE t';

 writeln (deri2str rtas);

 *)

 "-------- SK 060904 ----------------------------------------------";

 "----- order on polynomials -- input + output";

 val thy = @{theory "Isac"};

 val t = str2term "(a + -1 * b) / (-1 * a + b)";

 val SOME (t', _) = factout_p_ thy t; term2str t';

 val SOME (t', _) = cancel_p_ thy t; term2str t';

 val t = str2term "a*b*c*d / (d*e*f*g)";

 val SOME (t', _) = cancel_p_ thy t; term2str t';

 val t = str2term "a*(b*(c*d)) / (b*(e*(f*g)))";

 val SOME (t', _) = cancel_p_ thy t; term2str t';

 (*???order.SK  ???*)

 "----- SK060904-1a non-termination of cancel_p_ ? worked before 0707xx";

 val t = str2term "(x^^^2 - 4)*(3 - y) / ((y^^^2 - 9)*(2+x))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t; 

 if term2str t' = "(2 + -1 * x) / (3 + y)" then ()

 else error "rational.sml SK060904-1a worked since 0707xx";

 "----- SK060904-1b non-termination of cancel_p_ ... worked before 0707xx";

 val t = str2term ("(9 * a ^^^ 2 + -16 * b ^^^ 2) /" ^

 "(36 * a^^^2 * c + (27 * a^^^2 * e + (-64 * b^^^2 * c + -48 * b^^^2 * e)))");

 val SOME (t',_) = cancel_p_ thy t; 

 if term2str t' = "1 / (4 * c + 3 * e)" then ()

 else error "rational.sml SK060904-1b";

 "----- SK060904-2a non-termination of add_fraction_p_";

 val t = str2term (" (a + b * x) / (a + -1 * (b * x)) +  " ^

 		  " (-1 * a + b * x) / (a + b * x)      ");

 (* nonterm.SK

 val SOME (t',_) = rewrite_set_ thy false common_nominator_p t;

 common_nominator_p_ thy t;

 " (a + b * x)*(a + b * x) / ((a + -1 * (b * x))*(a + -1 * (b * x))) +  " ^

 " (-1 * a + b * x)*(a + -1 * (b * x)) / ((a + b * x)*(-1 * a + b * x)) ";

 add_fraction_p_ thy t; 

 " ((a + b * x)*(a + b * x)  +  (-1 * a + b * x)*(a + -1 * (b * x))) /" ^

 " ((a + b * x)*(-1 * a + b * x))                                     ";

 *)

 "-------- how to stepwise construct Scripts -------------";

 "-------- how to stepwise construct Scripts -------------";

 "-------- how to stepwise construct Scripts -------------";

 val thy = @{theory "Rational"};

 (*no trailing _*)

 val p1 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  (Rewrite_Set discard_minus False                   " ^

 "   t_t)");

 (*required (): (Rewrite_Set discard_minus False)*)

 val p2 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  (Rewrite_Set discard_minus False                   " ^

 "   t_t)");

 val p3 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  ((Rewrite_Set discard_minus False)                   " ^

 "   t_t)");

 val p4 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  ((Rewrite_Set discard_minus False)                   " ^

 "   t_t)");

 val p5 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  ((Try (Rewrite_Set discard_minus False)                   " ^

 "    Try (Rewrite_Set discard_parentheses False))               " ^

 "   t_t)");

 val p6 = parse thy (

 "Script SimplifyScript (t_t::real) =                             " ^

 "  ((Try (Rewrite_Set discard_minus False) @@                   " ^

 "    Try (Rewrite_Set rat_mult_poly False) @@                    " ^

 "    Try (Rewrite_Set make_rat_poly_with_parentheses False) @@   " ^

 "    Try (Rewrite_Set cancel_p_rls False) @@                     " ^

 "    (Repeat                                                     " ^

 "     ((Try (Rewrite_Set common_nominator_p_rls False) @@        " ^

 "       Try (Rewrite_Set rat_mult_div_pow False) @@              " ^

 "       Try (Rewrite_Set make_rat_poly_with_parentheses False) @@" ^

 "       Try (Rewrite_Set cancel_p_rls False) @@                  " ^

 "       Try (Rewrite_Set rat_reduce_1 False)))) @@               " ^

 "    Try (Rewrite_Set discard_parentheses False))               " ^

 "   t_t)"

 );

 "----------- get_denominator ----------------------------";

 "----------- get_denominator ----------------------------";

 "----------- get_denominator ----------------------------";

 val thy = @{theory Isac};

 val t = term_of (the (parse thy "get_denominator ((a +x)/b)"));

 val SOME (_, t') = eval_get_denominator "" 0 t thy;

 if term2str t' = "get_denominator ((a + x) / b) = b" then ()

 else error "get_denominator ((a + x) / b) = b"

 "--------- several errpats in complicated term -------------------";

 "--------- several errpats in complicated term -------------------";

 "--------- several errpats in complicated term -------------------";

 (*TODO: instead of Gabriella's example here (27.Jul.12) find a simpler one*)

 states:=[];

 CalcTree

 [(["Term ((5*b + 25)/(a^2 - b^2) * (a - b)/(5*b))", "normalform N"], 

   ("Rational",["rational","simplification"], ["simplification","of_rationals"]))];

 Iterator 1;

 moveActiveRoot 1;

 autoCalculate 1 CompleteCalc;

 val ((pt,p),_) = get_calc 1; show_pt pt;

 "-------- nonterminating cancel_p, norm_Rational 2002 ---";

 "-------- nonterminating cancel_p, norm_Rational 2002 ---";

 "-------- nonterminating cancel_p, norm_Rational 2002 ---";

 (*------------------------------------------------------------------------------------\

 "--- WN121204: searched rational.sml for "nonterm", added new numbering" ^

 "              and thoroughly tested with this numbering subsequently";

 "--- 1 ---";

 WN.2.6.03 from rlang.sml 56a 

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x) = 4 * (a * b) / (a ^^^ 2 + -1 * b ^^^ 2)";

 val NONE = rewrite_set_ thy false common_nominator_p t;

 "--- 2 ---";

 WN060831 nonterm.SK7 

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x)";

 val NONE = add_fraction_p_ thy t;

 "--- 3 ---";

 nonterm.SK9 loops: cancel_p kann nicht weiter kuerzen!!! *)

 val t'' = str2term "(a + b)/(x^^^2 - y^^^2) * ((x - y)^^^2/(a^^^2 - b^^^2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t'';

 "--- 4 ---";

 val t = str2term 

 "(a * x ^^^ 2 + -2 * a * x * y + a * y ^^^ 2 + b * x ^^^ 2 + -2 * b * x * y + b * y ^^^ 2) /(a ^^^ 2 * x ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 2 + -1 * b ^^^ 2 * x ^^^ 2 + b ^^^ 2 * y ^^^ 2)"; 

 WN060831 nonterm.SK10 

 val SOME (t,_) = rewrite_set_ thy false cancel_p t;

 term2str t;

 "--- 5 ---";

 val t = str2term 

 "(9*(x^^^2 - 8*x+16)/(4*(y^^^2 - 2*y+1)))/((3*x - 12)/(16*y - 16))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 if term2str t = 

 then ()

 else error "rational.sml: diff.behav. in norm_Rational_mg 42";

 "--- 6 ---";

 val t = str2term 

 "9*(x^^^2 - 8*x+16)*(16*y - 16)/(4*(y^^^2 - 2*y+1)*(3*x - 12))";

 val SOME (t',_) = rewrite_set_ thy false norm_Rational t;

 ... non terminating.

 "--- 7 ---";

 val SOME (t',_) = rewrite_set_ thy false make_polynomial t;

 "(-2304 + 1152 * x + 2304 * y + -144 * x ^^^ 2 + -1152 * x * y + 144 * x ^^^ 2 * y) /(-48 + 12 * x + 96 * y + -24 * x * y + -48 * y ^^^ 2 + 12 * x * y ^^^ 2)";

 val SOME (t,_) = rewrite_set_ thy false cancel_p t';

 "--- 8 ---";

 val t = str2term "(a-b)^^^3 * (x+y)^^^4 / ((x+y)^^^2 * (a-b)^^^5)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 "--- 9 ---";

 val t = str2term "((12*x*y/(9*x^^^2 - y^^^2))/" ^

 		 "(1/(3*x - y)^^^2 - 1/(3*x + y)^^^2)) *" ^

 		 "(1/(x - 5*y)^^^2 - 1/(x + 5*y)^^^2)/" ^

 		 "(20*x*y/(x^^^2 - 25*y^^^2))";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational(*_mg*) t;

 "--- 10 ---";

 SK060904-2a non-termination of add_fraction_p_";

 val t = str2term (" (a + b * x) / (a + -1 * (b * x)) +  " ^

 		  " (-1 * a + b * x) / (a + b * x)      ");

 (* nonterm.SK = WN130830

 val SOME (t',_) = rewrite_set_ thy false common_nominator_p t;

 "--- 11 ---";

 common_nominator_p_ thy t;

 " (a + b * x)*(a + b * x) / ((a + -1 * (b * x))*(a + -1 * (b * x))) +  " ^

 " (-1 * a + b * x)*(a + -1 * (b * x)) / ((a + b * x)*(-1 * a + b * x)) ";

 "--- 12 ---";                             

 add_fraction_p_ thy t; 

 " ((a + b * x)*(a + b * x)  +  (-1 * a + b * x)*(a + -1 * (b * x))) /" ^

 " ((a + b * x)*(-1 * a + b * x))                                     ";

 --------------------------------------------------------------------------------------/*)

 (*------------------------------------------------------------------------------------\

 "WN121205: thoroughly tested with the above numbering.";

 "  errors in cancel_p: --- 4,5,6,7.";

 "  error in common_nominator_p, common_nominator_p_: --- 10; 1,2?.";

 "  errors caused by ruleset norm_Rational: --- 8,9.";

 trace_rewrite := false;

 "--- 1 ---: non-terminating with ### add_fract: done t22 "; = WN130830

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x) = 4 * (a * b) / (a ^^^ 2 + -1 * b ^^^ 2)";

 trace_rewrite := false;

 rewrite_set_ thy false common_nominator_p t;

 "--- 2 ---: non-terminating with ### add_fract: done t22 ";

 val t = str2term "(a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x)";

 add_fraction_p_ thy t;

 "--- 3 ---: norm_Rational calls Rrls cancel_p with non-normalised polys";

 val t = str2term "(a + b)/(x^^^2 - y^^^2) * ((x - y)^^^2/(a^^^2 - b^^^2))";

 rewrite_set_ thy false norm_Rational t;

 (*tracing end...####  rls: cancel_p on: 

 (a * x ^^^ 2 + -2 * (a * (x * y)) + a * y ^^^ 2 + b * x ^^^ 2 + -2 * (b * (x * y)) + b * y ^^^ 2) /

 (a ^^^ 2 * x ^^^ 2 + -1 * (a ^^^ 2 * y ^^^ 2) + -1 * (b ^^^ 2 * x ^^^ 2) + b ^^^ 2 * y ^^^ 2) *)

 "--- 4 ---: non-terminating with Rrls cancel_p on plausible input";

 val t = str2term (

 "(a * x ^^^ 2 + -2 * a * x * y + a * y ^^^ 2 + b * x ^^^ 2 + -2 * b * x * y + b * y ^^^ 2) /"^

 "(a ^^^ 2 * x ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 2 + -1 * b ^^^ 2 * x ^^^ 2 + b ^^^ 2 * y ^^^ 2)"); 

 rewrite_set_ thy false cancel_p t;

 (*#  rls: cancel_p on: 

 (a * x ^^^ 2 + -2 * a * x * y + a * y ^^^ 2 + b * x ^^^ 2 + -2 * b * x * y + b * y ^^^ 2) /

 (a ^^^ 2 * x ^^^ 2 + -1 * a ^^^ 2 * y ^^^ 2 + -1 * b ^^^ 2 * x ^^^ 2 + b ^^^ 2 * y ^^^ 2) *)

 "--- 5 ---: non-terminating with Rrls cancel_p on plausible input";

 val t = str2term "(9*(x^^^2 - 8*x+16)/(4*(y^^^2 - 2*y+1)))/((3*x - 12)/(16*y - 16))";

 rewrite_set_ thy false norm_Rational t;

 (*####  rls: cancel_p on: 

 (2304 + -1152 * x + -2304 * y + 144 * x ^^^ 2 + 1152 * (x * y) + -144 * (x ^^^ 2 * y)) /

 (48 + -12 * x + -96 * y + 24 * (x * y) + 48 * y ^^^ 2 + -12 * (x * y ^^^ 2))  *)

 "--- 6 ---: non-terminating with Rrls cancel_p on plausible input";

 val t = str2term 

 "9*(x^^^2 - 8*x+16)*(16*y - 16)/(4*(y^^^2 - 2*y+1)*(3*x - 12))";

 rewrite_set_ thy false norm_Rational t;

 (*###  rls: cancel_p on: (-2304 + 1152 * x + 2304 * y + -144 * x ^^^ 2 + -1152 * (x * y) +

  144 * (x ^^^ 2 * y)) /

 (-48 + 12 * x + 96 * y + -24 * (x * y) + -48 * y ^^^ 2 + 12 * (x * y ^^^ 2)) *)

 "--- 7 ---: non-terminating with Rrls cancel_p on plausible input";

 val t' = str2term (

 "(-2304 + 1152 * x + 2304 * y + -144 * x ^^^ 2 + -1152 * x * y + 144 * x ^^^ 2 * y) /"^

 "(-48 + 12 * x + 96 * y + -24 * x * y + -48 * y ^^^ 2 + 12 * x * y ^^^ 2)");

 rewrite_set_ thy false cancel_p t';

 "--- 8 ---: bottom of output cannot be looked ad (due to looping?)";

 val t = str2term "(a-b)^^^3 * (x+y)^^^4 / ((x+y)^^^2 * (a-b)^^^5)";

 val SOME (t,_) = rewrite_set_ thy false norm_Rational t;

 "--- 9 ---: probably error in norm_Rational";

 val t = str2term (

 "((12*x*y / (9*x^^^2 - y^^^2)) / (1/(3*x - y)^^^2 - 1/(3*x + y)^^^2)) *" ^

 		"(1/(x - 5*y)^^^2 - 1/(x + 5*y)^^^2) / (20*x*y/(x^^^2 - 25*y^^^2))");

 rewrite_set_ thy false norm_Rational t;

 (*####  rls: cancel_p on: (19440 * (x ^^^ 8 * y ^^^ 2) + -490320 * (x ^^^ 6 * y ^^^ 4) +

  108240 * (x ^^^ 4 * y ^^^ 6) +

  -6000 * (x ^^^ 2 * y ^^^ 8)) /

 (2160 * (x ^^^ 8 * y ^^^ 2) + -108240 * (x ^^^ 6 * y ^^^ 4) +

  1362000 * (x ^^^ 4 * y ^^^ 6) +

  -150000 * (x ^^^ 2 * y ^^^ 8)) *)

 "--- 10 ---: non-terminating with ### add_fract: done t22: error in common_nominator_p ";

 val t = str2term (" (a + b * x) / (a + -1 * (b * x)) + (-1 * a + b * x) / (a + b * x)");

 rewrite_set_ thy false common_nominator_p t; (*### add_fract: done t22 *)

 common_nominator_p_ thy t;                   (*loops without output*)

 "--- reformulated 10:";

 val t = str2term "(a + -1 * (b * x)) / (a + b * x)";

 rewrite_set_ thy false cancel_p t = NONE;

 "--- 11 ---";

 "--- 12 ---";                             

 "...both are to be considered after common_nominator_p_ is improved";

 --------------------------------------------------------------------------------------/*)

 ============ inhibit exn WN130824 TODO ======================================================*)