[NTG-context] upload / metafun

[Hans Hagen]

Hi,

I uploaded a new lmtx. This time some work has been done at the metafun end.

At the tex end we're working on some overload protection mechanism which 
involves tagging many macro so that will take a while (most tagging is 
done but checking left over cases take time).

So, I wondered if we can do something similar in metapost: flag macros 
and variables in order to issue a warnings when a dangerous overload 
happens.

The current lmtx has this as an experiment: primitives, permanent, 
immutable and mutable (so far); you can look at the *.mpxl files to get 
an idea. If you say for instance

         path fullcircle;

there will be a warning

	metapost        > overloading immutable 'fullcircle'

or when

	\enabledirectives[metapost.overloadmode=error]

has been given you get an error.

The implementation is rather simple and non intrusive and differs from
the one in tex. There it is tightly integrated for all kind of reasons 
(millions of macro definitions per run so efficiency matters). Also, in 
metapost variables (tags) can have complex name constructions and we 
only test the top level. When a overload happens (overloadmode internal 
<> 0) a lua callback takes care of it.

A side effect is that we can query all hash entries and check for 
consistency which is what i've done and am doing now. Of course that can 
introduce issues ... just that you know.

Hans

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