Variable Name Lenth Limitation

[fsoubelet]

Hi,

I've noticed MAD-X crashes for inputs of variable names that are strictly longer than 47 characters. For instance, opening a MAD-X interpreter and entering this line will have it crash:

ATS_2022_05_08_B1_arc_by_arc_coupling_133cm_30cm = -1.0;

However, removing a single character to the variable name, which brings it to 47, works:

ATS_2022_05_08_B1_arc_by_arc_coupling_133cm_30c = -1.0;

We can also confirm this is not due to a limit on the line length, as the following works too (line of 97 characters):

arc_by_arc_coupling_133cm_30cm = 1.0 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1;

In the documentation, section 2.15 Variable Names there is no mention of such a limit. There is, however, mention of a limit at 17 or 48 in Chapter 16. Conversion to SixTrack with the LONG NAMES optional flag of the SIXTRACK command. It gives the impression that the limits is only for the export to SixTrack though, and not for MAD-X itself.

Is this a bug or a known limitation of MAD-X? If so, I would be ok making a small pull request adding the caveat to the documentation.