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MathGroup Archive 2007

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Re: Applying a list of functions to a single number

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74538] Re: Applying a list of functions to a single number
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 24 Mar 2007 05:25:39 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <eu1peu$eu1$1@smc.vnet.net>

siewsk at bp.com wrote:
> Applying a list of functions to a single number
> =================================
> 
> I have
> 
> Square[x_]:=x^2
> Cube[x_]:=x^3
> 
> I have tried
> 
> In[2]:={Square,Cube} @ 5
> 
> Out[2]:= {Square,Cube}[5]
> 
> But what I wanted is a list containing
> 
>  {25,125}
> 
> Obviously I'm doing this the wrong way. What is the correct way?
> 
> 

What you need is the function *Through* [1, 2]. For instance,

In[1]:=
square[x_] := x^2
cube[x_] := x^3
Through[{square, cube}[5]]

Out[3]=
{25, 125}

Note that Square (with a capital S) is already defined in Mathematica. 
Indeed, every Mathematica function starts with an uppercase letter (this 
is a convention established ages ago by Wolfram Research). To avoid any 
clash, it is better to use user-defined names starting with a lowercase 
letter.

Regards,
Jean-Marc

[1] http://documents.wolfram.com/mathematica/functions/Through

[2] "2.2.9 Advanced Topic: Working with Operators", 
http://documents.wolfram.com/mathematica/book/section-2.2.9


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