🚀 go-pugleaf

I've used zed.sty which I got from
ftp.comlab.ox.ac.uk:/pub/Zforum/zed.sty.

I found that \empty was defined as an empty set in
zed.sty, but it is the primitive in plain-TeX. So it
causes error when I use other style files that use
\empty as an empty token list.

I believe \empty shall not be redefined. The control
\empty must be defined as an empty token list at any
time. Therefore we don't use \empty as an empty set, but
\emptyset.

And then the following patch is to be applied to zed.sty
and zguide.tex.

--- zed.sty.dist	Thu Feb  9 14:16:52 1995
+++ zed.sty	Thu Feb  9 16:25:28 1995
@@ -145,7 +145,7 @@
 \def \ldata     {\langle\!\langle}
 \def \rdata     {\rangle\!\rangle}
 \let \shows	\vdash
-\@mc \empty	"0\@fy3F
+\@mc \emptyset	"0\@fy3F
 \let \rel	\leftrightarrow
 \def \dom	{\mathop{\rm dom}}
 \def \ran	{\mathop{\rm ran}}
--- zguide.tex.dist	Thu Feb  9 14:45:40 1995
+++ zguide.tex	Thu Feb  9 14:48:17 1995
@@ -382,7 +382,7 @@
 symbols defined as part of the mathematical tool-kit. First come the
 symbols which are not defined as infix operators, etc.:
 \begin{symtab}
-        \empty & \verb/\empty/ \\
+        \emptyset & \verb/\emptyset/ \\
 	\bigcup & \verb/\bigcup/ \\
 	\bigcap & \verb/\bigcap/ \\
 	\dom & \verb/\dom/ \\
@@ -569,13 +569,13 @@
 \begin{verbatim}
 \[
     \exists PhoneDB @ \\
-\t1     known = \empty
+\t1     known = \emptyset
 \]       
 \end{verbatim}
 \gives
 \[
     \exists PhoneDB @ \\
-\t1     known = \empty
+\t1     known = \emptyset
 \]       
 \end{demo}
 These commands generalize the standard \LaTeX\ commands with the same
--
ONO Kouichi