🚀 go-pugleaf

I am trying to use picTeX to draw a diagram like this

   .   	   .	   .	  .	 .	 .	 .	.	.
-20 10		-10 10		0 10		10 10         20 10 
   .   	   .	   .	  .	 .	 .	 .	.	.
-20 0		-10 0		0 0		10 0          20 0     

except that the actual diagram has some 100 points instead of 18 as in the
picture. (I know, I don't need picTeX for this, but I need it for
another purpose). 

The thing I find puzzling is this: 

++ If I issue the individual PiCTeX commands everything works fine
   (even for diagrams 4 times as large).

++ If I write two nested loops (as below), even bigTeX !!! (E. Mattes)
   chokes and complains about capacity exceeded. So the problem seems
   to lie with the loops, and not with picTeX being large, but who knows?

What is so taxing about a mere 100 points (right, points, ie \fiverm. ) and
200 numbers??

Julio Kuplinsky

=============================================================================

\input pictex
\newcount\xlimit\xlimit=30 
\newcount\ylimit\ylimit=30 
\newcount\x
\newcount\y
\newcount\gridstep\gridstep=5
\newcount\xlabelstep\xlabelstep=10
\newif\ifcontinue\continuetrue

\beginpicture
\setcoordinatesystem units < 1mm , 1mm >
\fiverm

\y=-\ylimit
\x=-\xlimit
\loop
  \loop
    \put{.} at {\x} {\y}
    \advance\x by \gridstep
    \ifnum\x > \xlimit \continuefalse\fi
    \ifcontinue %% NOTE: I have to use this stupid construct because
  \repeat       %% TeX won't allow \ifnum\x <= \xlimit. Am I mssng smthng?
\x=-\xlimit
\continuetrue
\advance\y by \gridstep
\ifnum\y > \ylimit \continuefalse\fi
\ifcontinue
\repeat

\continuetrue
\x=-\xlimit
\y=-\ylimit
\loop
  \loop
    \put{{\the\x} {\the\y}} <0mm,-1mm> at {\x} {\y}
    \advance\x by \xlabelstep
    \ifnum\x > \xlimit \continuefalse\fi
    \ifcontinue
  \repeat
  \x=-\xlimit
  \continuetrue
  \advance\y by \gridstep
  \ifnum\y > \ylimit\continuefalse\fi
  \ifcontinue
\repeat

\endpicture
\bye