vardef with @# not working within context

[Matthijs Kooijman <matthijs@stdin.nl>]

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Hi all,

I've been fiddling around with metaobj a bit, but defining my own objects
failed. After some debugging, I've reduced this to a metapost / context MkIV
issue (so no metaobj specifics anymore).

What happens, is that vardefs that use @# as a placeholder in their name only
work when they are defined in an external .mp file. When I define them inside
context (\startMPcode or \startMPinclusions), I get funny errors (mostly
"Isolated expression", which seems to mean that the macro is not defined).

I suspect this is because the way context extracts metapost code. Is this a
fundamental problem, or could it be fixed?

The following context file will easily reproduce the problem:

\starttext
\startMPcode
    vardef foo = draw (0mm,0mm)--(10mm,10mm); enddef;
    foo;

    vardef xy@# = (@#,@#) enddef ;
    draw xy0mm -- xy10mm; 
\stopMPcode
\stoptext

Running this file gives the following (first) error:
  mplib | mp terminal: >> xy0mm
  ! Improper `addto'.

To illustrate that this is specific to the use of @#, I've included the foo
vardef which does work properly. When I move the vardef xy.. line to a
separate file, say foo.mp, and replace it with "input foo;", the errors
disappear.

Gr.

Matthijs

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