Re: [Gnuplot-info] gnuplot hangs

[Thomas S. <t.s...@fz...>]

Leo Butler <l_butler <at> users.sourceforge.net> writes:

> 
> Hi,
> 
> The following bug was noted on the Maxima email list:
> 
> gnuplot> plot '-'
> input data ('e' ends) > -1. 1.
> input data ('e' ends) > 0. 0.99999999999999989
> input data ('e' ends) > e
>   C-c C-c^C
> 
>         G N U P L O T
>         Version 4.4 patchlevel 0
>         last modified March 2010
>         System: Linux 3.2.0-2-686-pae
> 

there should have been the message:

         warning: tick interval too small for machine precision

and internally the interval between the tics is set to
'end-start'.

but in this special case this is not sufficient, because (due
to machine precision) 'end' and 'start' are 1.0 and the step
size is 1.11022e-16
moreover, again due to machine precision.
1.0+1.11022e-16 is 1.0
so the tics generating loop never ends.

would something like this make sense in 'gen_tics()' in 'axis.c'?

for (tic = start; tic <= end; tic += step) {
    if (tic == tic+step) {
        int_warn(NO_CARET, "endless loop when generating tics, stopped");
        return;
    }
...
}