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MathGroup Archive 2002

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Re: Substitution!!!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35717] Re: Substitution!!!
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Sat, 27 Jul 2002 06:43:21 -0400 (EDT)
  • References: <ahlhov$s7t$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Previous responses have observed that getting the order of the rules correct
is the key to a solution.
This is clearly the right way for this problem. However I wondered what one
might do in general.
Here is a slower solution that uses Replace.

    fcts=(1+x) (1+x+x^2)(1+x+x^3)
(1+x+x^6)*(1+x^3+x^6)*(1+x+x^2+x^4+x^6)*(1+x+
          x^3+x^4+x^6)*(1+x+x^2+x^5+x^6);


rls=Thread[{1+x,1+x+x^2,1+x+x^3,1+x^2+x^3,1+x+x^6,1+x^3+x^6,1+x+x^2+x^4+x^6,
          1+x+x^3+x^4+x^6,1+x^5+x^6,1+x+x^2+x^5+x^6,1+x^2+x^3+x^5+x^6,
          1+x+x^4+x^5+x^6,1+x^2+x^4+x^5+x^6}\[Rule]{S01,S02,S03,S04,S05,S06,
          S07,S08,S09,S10,S11,S12,S13}];

Provided that there are two or more factors:

    rp1[p_,rls_]:=Replace[ p,rls,{1}]

    rp1[fcts, rls]

        S01 S02 S03 S05 S06 S07 S08 S10

If there may be only one factor:

    rp2[p_,rls_]:=Module[{a},{Replace[a p,rls,{1}],a=1}[[1]]]

    rp2[fcts, rls]

         S01 S02 S03 S05 S06 S07 S08 S10

--
Allan

---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565


"Chekad Sarami" <csarami at mtu.edu> wrote in message
news:ahlhov$s7t$1 at smc.vnet.net...
> Hi,
>
>
> I have a question regarding substitute of an expression with index
> variables..I need to make a table for some products of irreducible
> polynomials (Irreducible factors of x^63 -1) . But they are so large and I
> can't fit them into the columns of my table.  So I need to use these
> substitutions
>
> {S_1, S_2, S_3, S_4, S_5, S_6, S_7, S_8, S_9, S_10, S_11, S_12, S_13,
S_14}
> : ------>  {1 + x, 1 + x + x^2, 1 + x + x^3, 1 + x^2 + x^3, 1 + x + x^6,
>     1 + x^3 + x^6, 1 + x + x^2 + x^4 + x^6, 1 + x + x^3 + x^4 + x^6,  1 +
> x^5 + x^6, 1 + x + x^2 + x^5 + x^6,  1 + x^2 + x^3 + x^5 + x^6, 1 + x +
x^4
> + x^5 + x^6,   1 + x^2 + x^4 + x^5 + x^6}
>
>
>
> ***** The right side is a list of irreducible polynomials which is
assigned
> to {S_1, S_2,.... S_14}.*******
>
>
>
> For example instead of putting this large expression (1 + x)  (1 + x +
x^2)
> (1 + x + x^3) (1 + x + x^6) (1 + x^3 + x^6) (1 + x + x^2 + x^4 +  x\^6) (1
+
> x + x^3 + x^4 + x^6) (1 + x + x^2 + x^5 + x^6) in my table I can write it
in
> tems of S_i's  in this form  S_1 S_2 S_3 S_4 S_5 S_6 S_7 S_8.
>
>
>
> I tried ReplaceAll  but it changes  i.e. the above example to S_1
(S_1+x^3)
> (S_1+x_6) .... Which is not what I want.
>
> Can anybody tell me how to do this.
>
>
>
>
>
> Regards
>
> CHEKAD
>
>
>
>




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