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MathGroup Archive 2006

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Re: Function argument

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66991] Re: Function argument
  • From: Helen Read <hpr at together.net>
  • Date: Tue, 6 Jun 2006 06:27:55 -0400 (EDT)
  • References: <e60o3q$g5s$1@smc.vnet.net>
  • Reply-to: read at math.uvm.edu
  • Sender: owner-wri-mathgroup at wolfram.com

Bonny wrote:
> I would like to define a function g that evaluates another function f at a 
> given value. That is,
> 
> g[a, f[x]] := f[a]
> 
> For example, I might want the function f[x]=ax^2+bx+c to be evaluated at x=1 
> and get the result a+b+c. That is,
> 
> g[1, ax^2+bx+c] should evaluate to a+b+c.

Presumably you mean a x^2+b x + c, right? (Note the spaces between a and 
x^2, and between b and x).

> Again, I might want the function f[x]=Sin[x] to be evaluated at x=pi and get 

You mean x=Pi, right?

> the result 0. That is,
> 
> g[pi, Sin[x]] should evaluate to 0.
> 
> Is there a way to accomplish this in Mathematica? Any help would be 
> appreciated.

g[a_,f_]:=f/.{x->a}

will do what you want.

-- 
Helen Read
University of Vermont


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