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Re: How to map a list on function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97528] Re: How to map a list on function
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Sat, 14 Mar 2009 18:15:03 -0500 (EST)
  • References: <gpg18t$ceh$1@smc.vnet.net>

buts wrote:

> Hello,
>
> Could anyone explain me how to do the following:
> I have a long list of integer numbers in groups of four:
>
> list= {{10,3,5,7},{4,6,8,9},{0,8,3,6}, ...... }
>
> or its Flatten version.
>
> How to write a fast function g[list] which does this:
>
> g[list] =x^10*y^3*z^5*u^7 + x^4*y^6*z^8*u^9 + y^8*z^3*u^6+ ...
>
> It should be done many times (say, 10^4-6) on lists with length > 1000, so taking parts is not a good idea.
> How to use Map or similar ?
> Thanks.
>

I don't know if this is really fast, but it seems to work:

list = {{10, 3, 5, 7}, {4, 6, 8, 9}, {0, 8, 3, 6}, {4, 3, 5, 9}}

Plus @@ ((x^#1 + y^#2 + z^#3 + u^#4) & @@@ list)


Out= 1 + u^6 + u^7 + 2 u^9 + 2 x^4 + x^10 + 2 y^3 + y^6 +
    y^8 + z^3 + 2 z^5 + z^8
-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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