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RE: Function argument
*To*: mathgroup at smc.vnet.net
*Subject*: [mg66977] RE: [mg66953] Function argument
*From*: "Ingolf Dahl" <ingolf.dahl at telia.com>
*Date*: Tue, 6 Jun 2006 06:27:04 -0400 (EDT)
*Reply-to*: <ingolf.dahl at telia.com>
*Sender*: owner-wri-mathgroup at wolfram.com
Hi Bonny,
Maybe I am missing your point, but it not a good idea to have f[x] as the
second argument of g[a,f[x]]. Since we have not told which part of the
expression f[x] which is the function, and which part is the argument, we
will get into trouble if we substitute f1[f2[x]] as second argument to g.
Should it evaluate to f1[a], or to f1[f2[a]]? We also will get into trouble
in other cases. For instance, should the expression a x^2 + b x + c be seen
as a function of x, or of a, b or c?
You could define
g[a_, f_] := f[a]
if you are not satisfied with the usual notation f[a] or f@a. (What is wrong
with these notations?)
Then g[Pi, Sin] evaluates to 0. If you have set
f[x_] := a x^2 + b x + c
then g[1, f] will evaluate to a + b + c .
Also
g[1, Function[{x}, a x^2 + b x + c]] ,
g[1, (a #^2 + b # + c) &] ,
a x^2 + b x + c /. x -> 1
and
x=1; a x^2 + b x + c
will give this result, and there are surely a number of additional ways.
Best regards
Ingolf Dahl
Sweden
-----Original Message-----
From: Bonny [mailto:Banerjee at cse.ohio-state.edu]
To: mathgroup at smc.vnet.net
Subject: [mg66977] [mg66953] Function argument
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.
Again, I might want the function f[x]=Sin[x] to be evaluated at x=pi and get
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.
Thanks,
Bonny.
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