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Re: Variable number of arguments

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113341] Re: Variable number of arguments
  • From: Andy <andyr at wolfram.com>
  • Date: Sun, 24 Oct 2010 06:06:03 -0400 (EDT)

On 10/23/2010 6:04 AM, Sam Takoy wrote:
> Hi,
>
> I'm looking for help writing functions with variable number of arguments.
>
> For example, how do I accomplish the (rather artificial) task of writing
> the function FunnySum that:
> - When called with multiple arguments, sums them
> - When called with a list, sums the elements of the list
>
> I was hoping that the FunnySum1 below would work, but it doesn't
> multiple arguments. FunnySum2 works, but is that the best solution?
>
> FunnySum1[k__] := Apply[Plus, If[ListQ[k], Sequence[k], k]]
> FunnySum1[{1, 2, 3, 4, 5, 6}]
>
> FunnySum2[k__] := Plus[k]
> FunnySum2[k_List] := Apply[Plus, Sequence[k]]
> FunnySum2[1, 2, 3, 4, 5, 6]
> FunnySum2[{1, 2, 3, 4, 5, 6}]
>
> Many thanks in advance,
>
> Sam
>
You could use

FunnySum1[k__] := Apply[Plus, Sequence @@@ {k}]

If you want to ignore list structure altogether so that things like

FunnySum1[{1, {2,3},4},5] would give 15 you would need to use

Apply[ Plus, Flatten[ { k } ] ] instead.

-Andy




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