[metapost] Bug? Parsing def := := enddef;

[Nicola]

In article <Pine.LNX.4.61.1001211309560.9112 at linux.bop.eps.gda.pl>,
 Boguslaw Jackowski <B_Jackowski at GUST.org.pl> wrote:

> Hi,
> 
> Nicola:
> > according to The METAFONTbook, a macro definition can be 'def' followed 
> > by a symbolic token followed by either = or :=.
> [...]
> > But the following gives an error:
> > This is MetaPost, version 1.208 (kpathsea version 3.5.7dev)
> > **\relax
> > 
> > *def := := enddef;
> > ! Missing `=' has been inserted.
> > <to be read again> 
> >                    :=
> > <*> def := :=
> >               enddef;
> > ? 
> > That looks like a small bug.
> 
> Not sure. MF behaves similarly:
> 
>    This is METAFONT, Version 2.71828 (Web2c 7.5.2) (base=mf 2006.4.9)  21 JAN 
>    2010 13:06
>    (c:\TeXLive/texmf/web2c/cp8bit.tcx)
>    **zz.mf
>    (zz.mf
>    ! Missing `=' has been inserted.
>    <to be read again>
>                     :=
>    l.1 def := :=
>                enddef;
> 
> Was this behavior reported to Knuth?

Well, I haven't (yet). As I've said, this may be expected behaviour 
(otherwise, prof. Knuth could have defined (var)def's to just use '='). 
So, not sure it is worth filing a bug report.

Nicola