       Re: How to avoid repeated recalculation of the same function

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• Subject: [mg132677] Re: How to avoid repeated recalculation of the same function
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Sat, 3 May 2014 03:41:15 -0400 (EDT)
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```Did you try using Set ( = ) instead of SetDelayed ( := ) when defining f?  That is, try:

f[x_] = expression

On May 2, 2014, at 2:18 AM, pgeipi10 at 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
>

Murray Eisenberg                                murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 240 246-7240 (H)
University of Massachusetts
710 North Pleasant Street
Amherst, MA 01003-9305

```

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