[metapost] [mp-form.mp and negative numbers

[Stephan Hennig]

Hi,

I've noticed a problem with package graph not being able to format
negative numbers if package metafun is loaded.  I've noticed that
metafun comes with its own version of the format package, called
mp-form, that replaces format.  So I guess there must be a bug in
mp-form.mp.

In the attached code, if the metafun version of format is used, negative
numbers are prefixed by a string "unknown" instead of a minus sign.

Best regards,
Stephan Hennig

input metafun
% input format
prologues := 3;
beginfig(1);
  label(format("%3f", 1234), (50,100));
  label(format("%3f", -1234), (50,50));
endfig;
end