Re: [sc-dev] frac semantic

[Scott Carver <scott@xxxxxxxxxxxxx>]

The lang version of .frac is equivalent to n%1. In terms of usefulness, then, it might be better to go with the ugen definition of .frac, so both possibilities are covered.

- Scott

On Dec 17, 2009, at 10:33 AM, Tim Blechmann wrote:

> according to the supercollider docs, the frac operator is defined as:
> frac .. fractional part [1]
> 
> the unit generator implements it as defined in wikipedia (according to
> Graham, Knuth, & Patashnik) [2]:
> x - floor(x)
> 
> the language as defined at wolfram [3] and the c99 modf function [4]:
> x - trunc(x)
> 
> for positive x, the result is the same, for negative x, the first
> formula returns positive values, the second version negative values.
> 
> 
> the only version, where this is actually used in the class library is
> the implementation of LinLin. for this use case, the implementation
> doesn't matter though:
> ^LinLin.ar(in.frac, 0.0, 1.0, val0, val1);
> ^LinLin.kr(in.frac, 0.0, 1.0, val0, val1);
> 
> 
> although i don't like breaking backwards compatibility, i think, it is
> useful here in order a consistent behavior in language and server.
> especially since the specification is not precise. it shouldn't touch
> too much code and if people made use of it, i hope, they were aware of
> the imprecise specification. personally i am not sure about the best
> definition, though ... while i like using the definitions, used by
> mathematicians, i also like the consistency with modf.
> 
> so, i'd be curious to hear thoughts about this ...
> 
> tim
> 
> 
> [1] build/Help/Language/Operators.html
> [2] http://en.wikipedia.org/wiki/Floor_and_ceiling_functions#Fractional_part
> [3] http://mathworld.wolfram.com/FractionalPart.html
> [4] http://opengroup.org/onlinepubs/007908799/xsh/modf.html
> 
> 
> -- 
> tim@xxxxxxxxxx
> http://tim.klingt.org
> 
> It is better to make a piece of music than to perform one, better to
> perform one than to listen to one, better to listen to one than to
> misuse it as a means of distraction, entertainment, or acquisition of
> 'culture'.
> John Cage
> 
> 


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