From the documentation:

real modf(real x, ref real y);

why is y a ref parameter?

http://www.digitalmars.com/d/1.0/phobos/std_math.html

Spacen Jasset wrote:
>  From the documentation:
> 
> real modf(real x, ref real y);
> 
> why is y a ref parameter?
> 
> http://www.digitalmars.com/d/1.0/phobos/std_math.html

Apparently it doesn't do what it says it does. The implementation simply calls std.c.math.modfl(x, &y), which is documented at <http://www.opengroup.org/onlinepubs/000095399/functions/modf.html>.

Apparently, std.math.modf(x,y), which is documented to return the remainder of (x / y), actually returns the fractional part of x, storing the integral part in y (so it never even *reads* y).

Now, I can't remember ever using anything in std.math that takes > 1 parameter (mostly abs, sqrt, etc.) and haven't even executed modf(), but this seems to be a bug in either the documentation or the implementation of this function.
Cross-posted to d.D.bugs & follow-up set.