[metapost] [bug] documentation of length operator

[Stephan Hennig]

Hi,

although I didn't find anything about that in mpman and mpgraph the
length operator is perfectly happy operating on strings:

beginfig(1);
string s;
  s := "MetaPost";
  show length(s);
endfig;
end

If this feature is officially supported, it is missing from mpman, that
only discusses "length <path primary>".  Mpgraph adds to that only
"length <picture primary>".

Best regards,
Stephan Hennig