I've been trying to generate a new kind of pattern by use of macros and am
unable to use the individual coordinates of the point being evaluated for
the pattern.

This works:

#macro crn()
  (x - int(x))
#end

This does not:
#macro crn()
  #declare a = int(x);
  (x - a)
#end

Why?

What I want to do is get the x, y, and z values of the point being evaluated
by pigment{function{crn()} and use them as they were floats, not vectors.
I need them for array indices as my noise resembles Perlin in its
calculation, but uses a catmull-rom spline (smoother noise, more control
points) instead of cubic.

Some years ago I modified Povray source, swapping the internal noise
function for the catmull-rom version, but I could only compile in DOS.  I
tried to get it into MegaPov but the development of Povray 3.5 prevented
it.

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