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Re: Map[] and multiple args function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96261] Re: Map[] and multiple args function
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Tue, 10 Feb 2009 05:53:16 -0500 (EST)
  • References: <gmp0ps$c0a$1@smc.vnet.net>

You should use Apply (@@) instead of Map (/@). Otherwise, Foo is
working on an array instead of on three arguments. Given the level at
which it is needed ({1}) you could use the @@@ version of Apply.

The Plus & Sequence stuff works but its better to use Total

Foo @@@ {{1, 2, 3}, {4, 5, 6}} // Total

Cheers -- Sjoerd

On Feb 9, 12:33 pm, sagra... at gmail.com wrote:
> I know this has to be FAQ, but I'm just not able to find an answer
> anywhere, so - here it goes:  I have a multiple-arguments function,
> say something like:
>    Foo[x_, y_, z_] := x + 2*y + 3*z
> Now, I want to call this function number of times, over different sets
> of arguments, and then to sum results.  I thought about storing
> argument triplets into some kind of list, and then employing sequence
> of Map[] and Apply[] to get the job done.  After number of trials and
> errors, I came up with following piece of code doing the thing:
>   Plus @@ Foo /@ {{1, 2, 3}, {4, 5, 6}} /. List -> Sequence
> but I even don't fully understand what's going here, and also I'm
> wondering is there a "better" way to accomplish this.  So - any
> suggestion?
>
> Thanks.



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