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From: Bob Hanlon <hanlonr357@gmail.com>
Newsgroups: comp.soft-sys.math.mathematica
Subject: Re: How to avoid repeated recalculation of the same function
Date: Sat, 3 May 2014 07:40:33 +0000 (UTC)
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If the calculation can be done symbolicly use f[x_] = calc rather than
f[x_] := calc

You may also want to [Full]Simplify the expression, i.e., f[x_] = Simplify[
calc, assumptions ] to speed up subsequent use as well as improve numerical
precision.


Bob Hanlon



On Fri, May 2, 2014 at 2:18 AM, <pgeipi10@gmail.com> wrote:

> Hi,
>
> I'm doing a calculaton that's purly symbolic (no graphing, numerical
> integration, etc.).
>
> Suppose I have a function f[x_]:=... that's very complex to build. In
> fact, f[x] ends up being a manageable expression (about 30 characters) but
> it takes Mathematica about 30 min to build that expression.
>
> Another function g[] uses the function f[x] and references it many times.
> I've discovered that g[] actually builds f[x] every time it's referenced
> which takes 30 minutes each time. Theoretically, Mathematica could build it
> once and then use the resulting expression every time it's referenced.
>
> So how do I accomplish that? That is, how do I make it build f[x] once and
> then use the resulting expression when it's needed?
>
> Thanks,
>
>
> Pavel
>
>