[PD] [OT] "processing" application

Mathieu Bouchard matju at artengine.ca
Sat Oct 14 13:24:14 CEST 2006

On Fri, 13 Oct 2006, David Powers wrote:

> When working with computers, I think you'd also want to point out that a 
> 'float' has some amount of precision, and that this is related to how 
> many bits of memory the computer uses to store the number.


> I believe it would be correct to say a float is a finite decimal 
> approximation

No, it's a binary approximation, which is not equivalent to a decimal 
approximation because the bases do not have the same prime factors. In 
that sense, base 8 and 16 are equivalent to each other, and bases 10 and 
20 and 50 are equivalent, but the two groups of bases are not, because one 
is 2^a and the other is 2^a * 5^b. (a,b must be more than zero of course, 
else they'd be the same for b=0).

> Anyway, knowing that the number is a decimal approximation might be 
> important from time to time in multimedia programming...

Knowing that it's not a decimal approximation might be important, at least 
for the fact that most of the time 1 - 0.9 is not exactly 0.1, when you 
ask pd or most any other piece of software.

You may also use true rationals in some languages, so that 1 - 9/10 is 
always exactly 1/10, but it's a lot slower, and it's not available in pd 
yet. (It's available in Lisp, Smalltalk, Ruby, Mathematica, and a bunch 

  _ _ __ ___ _____ ________ _____________ _____________________ ...
| Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju
| Freelance Digital Arts Engineer, Montréal QC Canada

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