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AppGameKit Classic Chat / c++ exp() - how to in AGK?

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nz0
AGK Developer
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Posted: 29th May 2013 21:27
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I've been looking for a way to duplicate the exp() function of c++.

This is the exponential function of x.

I have looked around and think that Euler's number e can be used as a constant somewhere in the calculation.

Haven't been able to see a breakdown of this function (that I could understand anyway).

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Naphier
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Location: St Petersburg, Florida
Posted: 29th May 2013 23:40
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It is just e^x
according to
http://www.cplusplus.com/reference/cmath/exp/

I do wonder how long e is in the c++ function.

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nz0
AGK Developer
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Posted: 30th May 2013 00:03
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e, I gather is euler's number - let's say 2.7182818284590452353602874713527 - apparently it's been computed to a trillion places

So, seeing as exp(5.0) is supposed return 148.413159 according to that example, I tried it in AGK.. and ...

I get 79.432350

Same if I use the windows CALC to work it out..

Oh.. hang on - did it back to front - haha.. x^e

Well, AppGameKit returns 148.413132. This is probably down to the precision of the e value, but hey - it works - thanks for the reply.

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Hodgey
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Posted: 30th May 2013 00:04
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Quote: "I do wonder how long e is in the c++ function."

It's probably #defined somewhere and so will be used as a double. In AppGameKit we're limited to 32 bit floats.

So a basic exp function would go like this:
#constant E 2.71828

Function exp(x as float)
result# = E^x
Endfunction result#

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nz0
AGK Developer
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Posted: 30th May 2013 00:19
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Yep, that all fits together. Wasn't sure what precision we were stuck with in AGK.

I'm sure it will be precise enough though.

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