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MathGroup Archive 2004

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Re: Forcing Argument Evaluation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49881] Re: [mg49848] Forcing Argument Evaluation
  • From: "David Park" <djmp at earthlink.net>
  • Date: Thu, 5 Aug 2004 09:20:50 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Scott,

If you want to use operators this way you might want to look at the
Algebra`PushThrough package at my web site below.

Needs["Algebra`PushThrough`"]

f[x_] := x^2;

{f, f/2}[2]
% // PushThrough[]
{f, f/2}[2]
{4, 2}

Whereas if you use the regular Through command you get

{f, f/2}[2] // Through
{4, (f/2)[2]}

Similarly

(f/2)[2] // Through
4*(1/2)[2]

Through pushed the argument 2 onto f AND onto (1/2).

(f/2)[2] // PushThrough[]
2

Also

(f/a)[2] // PushThrough[Constants -> {a}]
4/a

(f^2 - 2*f)[x]//PushThrough[]
-2*x^2 + x^4

but

(f^2 - 2f)[x] // Through
(-2*f)[x] + (f^2)[x]


David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/



From: Scott Guthery [mailto:sguthery at mobile-mind.com]
To: mathgroup at smc.vnet.net

f[x_] := x^2;
a = {f,f/2};

a[[1]][2]
4

a[[2]][[2]
f/2[2]

I know I'm missing something fundamental.

Cheers, Scott







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