strange behaviour with simple decimals



On 4/18/07, Barton Willis <willisb at unk.edu> wrote:
>
> (%i1) 1/(abs(1+2*g) - abs(2*g))$
> (%i2) plot2d(%,[g,0,19]);
>

The 'abs' and the multiplication aren't actually the issue.  A simpler
example:

        plot2d( '(0,1+g)-g,[g,0,200],[nticks,1000]);

The '(0,...) construction blocks simplification.

Not by coincidence, this happens in the intervals [2^n-1,2^n].  With a
different base, it would happen at [base^n-1,base^n].  Of course, with exact
arithmetic, it doesn't happen.

The only complaint I have about Maxima here is that its plotting routines
aren't clever enough to realize that a seemingly isolated blip should be
investigated further.  But perhaps it is noticing that the blip is so tiny
that it is probably a calculation error (which it is...).

            -s