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MathGroup Archive 2010

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Checking variables in an expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112454] Checking variables in an expression
  • From: Ignacio Plazeta <Ignacio.Plazeta at speednet.es>
  • Date: Thu, 16 Sep 2010 05:58:57 -0400 (EDT)

Dear Friends


While having the lunch break I thought up this trick
that, may be, substantially solves (making use of Complement ...)
the problem I posed in my previous post.

Do you see any fault or improvement ? Thanks !


myChecker[myExp_] := Module [{tmp},
   myF[myArg_] := Module [{tmp2},
     tmp2 = {};
     Scan[(AppendTo[tmp2, Apply[List, #]]) &, myArg];
     tmp2 = Flatten[tmp2, Infinity] // Union;
     Return[tmp2];
     ];
   tmp = FixedPoint[myF, myExp];
   tmp = Select[tmp, (Head[#] === Symbol) &];
   Return[tmp];
   ]
myChecker[a + b]
myChecker[2 a^ 3 b]


Best Reagards
Ignacio


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