# HG changeset patch
# User wenzelm
# Date 856448117 -3600
# Node ID 13ba951a457214186029859c69147ae9191d39c6
# Parent  448bb82c40035955f9adf34d0067bb1438880155
added this file;

diff -r 448bb82c4003 -r 13ba951a4572 doc-src/rail.sty
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc-src/rail.sty	Thu Feb 20 15:15:17 1997 +0100
@@ -0,0 +1,890 @@
+% rail.sty - style file to support railroad diagrams
+%
+% 09-Jul-90 L. Rooijakkers
+% 08-Oct-90 L. Rooijakkers	fixed centering bug when \rail@tmpc<0.
+% 07-Feb-91 L. Rooijakkers	added \railoptions command, indexing
+% 08-Feb-91 L. Rooijakkers	minor fixes
+%
+% This style file needs to be used in conjunction with the 'rail'
+% program. Running LaTeX as 'latex file' produces file.rai, which should be
+% processed by Rail with 'rail file'. This produces file.rao, which will
+% be picked up by LaTeX on the next 'latex file' run.
+%
+% LaTeX will warn if there is no file.rao or it's out of date.
+%
+% The macros in this file thus consist of two parts: those that read and
+% write the .rai and .rao files, and those that do the actual formatting
+% of the railroad diagrams.
+
+% railroad read/write macros
+%
+% \begin{rail} TEXT \end{rail} : TEXT is written out to the .rai file,
+%                                as \rail@i{NR}{TEXT}. Then the matching
+%                                \rail@o{NR}{FMT} from the .rao file is
+%                                executed (if defined).
+%
+% \railoptions{OPTIONS} : OPTIONS are written out to the .rai file,
+%                         as \rail@p{OPTIONS}.
+%
+% \railterm{IDENT,IDENT,...} : format IDENT as terminals. writes out
+%                              \rail@t{IDENT} to the .rai file and
+%                              defines \rail@t@IDENT as \rail@termfont IDENT.
+%
+% \railtoken{IDENT}{TEXT} : format IDENT as terminal TEXT. writes out
+%                           \rail@t{IDENT} to the .rai file and defines
+%                           \rail@t@IDENT as TEXT.
+%
+% \rail@nr : railroad diagram counter, starts at 1
+%
+% \ifrail@match : current \rail@i{NR}{TEXT} matches
+%
+% \rail@first :	actions to be done first. read in .rao file,
+%               open .rai file if \@filesw true, undefine \rail@first.
+%               executed from \begin{rail} and \railtoken.
+%
+% \rail@i{NR}{TEXT} : defines \rail@i@NR as TEXT. written to the .rai
+%                     file by \rail, read from the .rao file by
+%                     \rail@first
+%
+% \rail@t{IDENT} : tells Rail that IDENT is to be custom formatted,
+%                  written to the .rai file by \railterm and \railtoken.
+%
+% \rail@o{NR}{TEXT} : defines \rail@o@NR as TEXT, read from the .rao
+%                     file by \rail@first.
+%
+% \rail@p{OPTIONS} : pass options to rail, written to the .rai file by
+%                    \railoptions
+%
+% \rail@warn : warn user for mismatching diagrams
+%
+% \rail@endwarn : either \relax or \rail@warn
+%
+% \rail@enddocument : original \enddocument
+%
+% \enddocument : checks \ifrail@all
+
+\newcount\rail@nr
+\rail@nr=1
+
+\newif\ifrail@all
+\rail@alltrue
+
+\newif\ifrail@match
+
+\def\rail@first{
+\makeatletter
+\@input{\jobname.rao}
+\makeatother
+\if@filesw
+\newwrite\tf@rai
+\immediate\openout\tf@rai\jobname.rai\relax
+\fi
+\global\let\rail@first=\relax
+}
+
+\long\def\rail#1\end#2{
+\end{#2}
+\rail@first
+\begingroup
+\let\\=\relax
+\global\edef\rail@i@{#1}
+\endgroup
+\@ifundefined{tf@rai}{}{
+\begingroup
+\let\\=\relax
+\immediate\write\tf@rai{\noexpand\rail@i{\number\rail@nr}{\rail@i@}}
+\endgroup
+}
+\rail@matchtrue
+\@ifundefined{rail@o@\number\rail@nr}{\rail@matchfalse}{}
+\expandafter\ifx\csname rail@i@\number\rail@nr\endcsname\rail@i@
+\else
+\rail@matchfalse
+\fi
+\ifrail@match
+\expandafter\relax\csname rail@o@\number\rail@nr\endcsname
+\else
+\@warning{Railroad diagram {\number\rail@nr} doesn't match}
+\global\let\rail@endwarn=\rail@warn
+\rail@begin{1}{}
+\rail@setbox{\bf ???}
+\rail@oval
+\rail@end
+\fi
+\global\advance\rail@nr by 1
+}
+
+\def\railoptions#1{
+\rail@first
+\@writefile{rai}{\noexpand\rail@p{#1}}
+}
+
+\def\railterm#1{
+\rail@first
+\@for\rail@i@:=#1\do{
+\@writefile{rai}{\noexpand\rail@t{\rail@i@}}
+}
+}
+
+\def\railtoken#1#2{
+\rail@first
+\@writefile{rai}{\noexpand\rail@t{#1}}
+\expandafter\def\csname rail@t@#1\endcsname{#2}
+}
+
+\long\def\rail@i#1#2{
+\expandafter\gdef\csname rail@i@#1\endcsname{#2}
+}
+
+\def\rail@o#1#2{
+\expandafter\gdef\csname rail@o@#1\endcsname{#2}
+}
+
+\def\rail@t#1{}
+
+\def\rail@p#1{}
+
+\def\rail@warn{
+\@warning{Railroad diagram(s) may have changed. Use 'rail' and rerun}
+}
+
+\let\rail@endwarn=\relax
+
+\let\rail@enddocument=\enddocument
+
+\def\enddocument{
+\rail@endwarn
+\rail@enddocument
+}
+
+% index entry macro
+%
+% \rail@index{IDENT} : add index entry for IDENT
+
+\def\rail@index#1{
+\index{\rail@indexfont#1}
+}
+
+% railroad diagram formatting parameters (user level)
+% all of these are copied into their internal versions by \railinit
+%
+% \railunit : \unitlength within railroad diagrams
+% \railextra : extra length at outside of diagram
+% \railboxheight : height of ovals and frames
+% \railboxskip : vertical space between lines
+% \railboxleft : space to the left of a box
+% \railboxright : space to the right of a box
+% \railovalspace : extra space around contents of oval
+% \railframespace : extra space around contents of frame
+% \railtextleft : space to the left of text
+% \railtextright : space to the right of text
+% \railtextup : space to lift text up
+% \railjoinsize : circle size of join/split arcs
+% \railjoinadjust : space to adjust join
+%
+% \railnamesep : separator between name and rule body
+
+\newdimen\railunit
+\newdimen\railextra
+\newdimen\railboxheight
+\newdimen\railboxskip
+\newdimen\railboxleft
+\newdimen\railboxright
+\newdimen\railovalspace
+\newdimen\railframespace
+\newdimen\railtextleft
+\newdimen\railtextright
+\newdimen\railtextup
+\newdimen\railjoinsize
+\newdimen\railjoinadjust
+\newdimen\railnamesep
+
+% internal versions of the formatting parameters
+%
+% \rail@extra   : \railextra
+% \rail@boxht   : \railboxheight
+% \rail@boxsp   : \railboxskip
+% \rail@boxlf   : \railboxleft
+% \rail@boxrt   : \railboxright
+% \rail@boxhht  : \railboxheight / 2
+% \rail@ovalsp  : \railovalspace
+% \rail@framesp : \railframespace
+% \rail@textlf	: \railtextleft
+% \rail@textrt	: \railtextright
+% \rail@textup	: \railtextup
+% \rail@joinsz  : \railjoinsize
+% \rail@joinhsz : \railjoinsize / 2
+% \rail@joinadj : \railjoinadjust
+%
+% \railinit : internalize all of the parameters.
+
+\newcount\rail@extra
+\newcount\rail@boxht
+\newcount\rail@boxsp
+\newcount\rail@boxlf
+\newcount\rail@boxrt
+\newcount\rail@boxhht
+\newcount\rail@ovalsp
+\newcount\rail@framesp
+\newcount\rail@textlf
+\newcount\rail@textrt
+\newcount\rail@textup
+\newcount\rail@joinsz
+\newcount\rail@joinhsz
+\newcount\rail@joinadj
+
+\def\railinit{
+\rail@extra=\railextra
+\divide\rail@extra by \railunit
+\rail@boxht=\railboxheight
+\divide\rail@boxht by \railunit
+\rail@boxsp=\railboxskip
+\divide\rail@boxsp by \railunit
+\rail@boxlf=\railboxleft
+\divide\rail@boxlf by \railunit
+\rail@boxrt=\railboxright
+\divide\rail@boxrt by \railunit
+\rail@boxhht=\railboxheight
+\divide\rail@boxhht by \railunit
+\divide\rail@boxhht by 2
+\rail@ovalsp=\railovalspace
+\divide\rail@ovalsp by \railunit
+\rail@framesp=\railframespace
+\divide\rail@framesp by \railunit
+\rail@textlf=\railtextleft
+\divide\rail@textlf by \railunit
+\rail@textrt=\railtextright
+\divide\rail@textrt by \railunit
+\rail@textup=\railtextup
+\divide\rail@textup by \railunit
+\rail@joinsz=\railjoinsize
+\divide\rail@joinsz by \railunit
+\rail@joinhsz=\railjoinsize
+\divide\rail@joinhsz by \railunit
+\divide\rail@joinhsz by 2
+\rail@joinadj=\railjoinadjust
+\divide\rail@joinadj by \railunit
+}
+
+% initialize the parameters
+
+\railunit=1sp
+\railextra=4ex
+\railboxleft=1ex
+\railboxright=1ex
+\railovalspace=2ex
+\railframespace=2ex
+\railtextleft=1ex
+\railtextright=1ex
+\railjoinadjust=0pt
+\railnamesep=1ex
+
+\ifcase\@ptsize
+% 10 pt
+\railboxheight=16pt
+\railboxskip=24pt
+\railtextup=5pt
+\railjoinsize=16pt
+\or
+% 11 pt
+\railboxheight=16pt
+\railboxskip=24pt
+\railtextup=5pt
+\railjoinsize=16pt
+\or
+% 12 pt
+\railboxheight=20pt
+\railboxskip=28pt
+\railtextup=6pt
+\railjoinsize=20pt
+\fi
+
+\railinit
+
+% railroad formatting primitives
+%
+% \rail@x : current x
+% \rail@y : current y
+% \rail@ex : current end x
+% \rail@sx : starting x for \rail@cr
+% \rail@rx : rightmost previous x for \rail@cr
+%
+% \rail@tmpa : temporary count
+% \rail@tmpb : temporary count
+% \rail@tmpc : temporary count
+%
+% \rail@put : put at (\rail@x,\rail@y)
+%
+% \rail@eline : end line by drawing from \rail@ex to \rail@x
+%
+% \rail@sety{LEVEL} : set \rail@y to level LEVEL
+
+\newcount\rail@x
+\newcount\rail@y
+\newcount\rail@ex
+\newcount\rail@sx
+\newcount\rail@rx
+
+\newcount\rail@tmpa
+\newcount\rail@tmpb
+\newcount\rail@tmpc
+
+\def\rail@put{\put(\number\rail@x,\number\rail@y)}
+
+\def\rail@eline{
+\rail@tmpb=\rail@x
+\advance\rail@tmpb by -\rail@ex
+\rail@put{\line(-1,0){\number\rail@tmpb}}
+}
+
+\def\rail@sety#1{
+\rail@y=#1
+\multiply\rail@y by -\rail@boxsp
+\advance\rail@y by -\rail@boxht
+}
+
+% \rail@list : declarations for list environment
+%
+% \railparam{TEXT} : sets \rail@list to TEXT
+%
+% \rail@begin{HEIGHT}{NAME} : begin a railroad diagram of height HEIGHT
+%
+% \rail@end : end a railroad diagram
+
+\def\rail@list{}
+
+\def\railparam#1{
+\def\rail@list{#1}
+}
+
+\newbox\tempbox
+
+\def\rail@begin#1#2{
+\medskip
+\begin{list}{}{\rail@list}
+\item[]
+\vbox\bgroup
+\ifx\@empty#2\else
+{\rail@namefont #2}
+\\*[\railnamesep]\nopagebreak
+\fi
+\unitlength=\railunit
+\rail@tmpa=#1
+\multiply\rail@tmpa by \rail@boxsp
+\begin{picture}(0,\number\rail@tmpa)(0,-\number\rail@tmpa)
+\rail@ex=0
+\rail@rx=0
+\rail@x=\rail@extra
+\rail@sx=\rail@x
+\rail@sety{0}
+}
+
+\def\rail@end{
+\advance\rail@x by \rail@extra
+\rail@eline
+\end{picture}
+\egroup
+\end{list}
+}
+
+% \rail@tokenfont : format setup for \railtoken identifiers
+%
+% \rail@termfont : format setup for terminals
+%
+% \rail@nontfont : format setup for nonterminals
+%
+% \rail@annofont : format setup for annotations
+%
+% \rail@rulefont : format setup for rule names
+%
+% \rail@indexfont : format setup for index entry
+%
+% \railtokenfont{TEXT} : set \railtoken format setup to TEXT
+%
+% \railtermfont{TEXT} : set terminal format setup to TEXT
+%
+% \railnontermfont{TEXT} : set nonterminal format setup to TEXT
+%
+% \railannotatefont{TEXT} : set annotation format setup to TEXT
+%
+% \railnamefont{TEXT} : set rule name format setup to TEXT
+%
+% \railindexfont{TEXT} : set index entry format setup to TEXT
+
+\let\rail@tokenfont=\tt
+\let\rail@termfont=\tt
+\let\rail@nontfont=\rm
+\let\rail@annofont=\it
+\let\rail@namefont=\it
+\let\rail@indexfont=\it
+
+\def\railtokenfont#1{
+\def\rail@tokenfont{#1}
+}
+
+\def\railtermfont#1{
+\def\rail@termfont{#1}
+}
+
+\def\railnontermfont#1{
+\def\rail@nontfont{#1}
+}
+
+\def\railannotatefont#1{
+\def\rail@annofont{#1}
+}
+
+\def\railnamefont#1{
+\def\rail@namefont{#1}
+}
+
+\def\railindexfont#1{
+\def\rail@indexfont{#1}
+}
+
+% \rail@token{TEXT} : format token TEXT
+%
+% \rail@ctoken{TEXT} : format token TEXT centered
+%
+% \rail@nont{TEXT} : format nonterminal TEXT
+%
+% \rail@cnont{TEXT} : format nonterminal TEXT centered
+%
+% \rail@cterm{TEXT} : format terminal TEXT
+%
+% \rail@cterm{TEXT} : format terminal TEXT centered
+%
+% \rail@annote[TEXT] : format TEXT as annotation
+%
+% \rail@annotebox[TEXT] : annotate box with TEXT
+
+\def\rail@token#1{
+\expandafter\@ifundefined{rail@t@#1}{
+\rail@setbox{\rail@termfont #1}
+}{
+\rail@setbox{\rail@tokenfont \csname rail@t@#1\endcsname}
+}
+\rail@oval
+}
+
+\def\rail@ctoken#1{
+\rail@setbox{\rail@tokenfont \csname rail@t@#1\endcsname}
+\rail@coval
+}
+
+\def\rail@nont#1{
+\rail@setbox{\rail@nontfont #1}
+\rail@frame
+}
+
+\def\rail@cnont#1{
+\rail@setbox{\rail@nontfont #1}
+\rail@cframe
+}
+
+\def\rail@term#1{
+\rail@setbox{\rail@termfont #1}
+\rail@oval
+}
+
+\def\rail@cterm#1{
+\rail@setbox{\rail@termfont #1}
+\rail@coval
+}
+
+\def\rail@annote[#1]{
+\rail@setbox{\rail@annofont #1}
+\rail@text
+}
+
+\def\rail@annotebox[#1]{
+\ \rail@annofont #1
+}
+
+% \rail@box : temporary box for \rail@oval and \rail@frame
+%
+% \rail@setbox{TEXT} : set \rail@box to TEXT, set \rail@tmpa to width
+%
+% \rail@oval : format \rail@box of width \rail@tmpa inside an oval
+%
+% \rail@coval : same as \rail@oval, but centered between \rail@x and
+%               \rail@mx
+%
+% \rail@frame : format \rail@box of width \rail@tmpa inside a frame
+%
+% \rail@cframe : same as \rail@frame, but centered between \rail@x and
+%                \rail@mx
+%
+% \rail@text : format \rail@box of width \rail@tmpa above the line
+
+\newbox\rail@box
+
+\def\rail@setbox#1{
+\setbox\rail@box\hbox{\strut#1}
+\rail@tmpa=\wd\rail@box
+\divide\rail@tmpa by \railunit
+}
+
+\def\rail@oval{
+\advance\rail@x by \rail@boxlf
+\rail@eline
+\advance\rail@tmpa by \rail@ovalsp
+\ifnum\rail@tmpa<\rail@boxht\rail@tmpa=\rail@boxht\fi
+\rail@tmpb=\rail@tmpa
+\divide\rail@tmpb by 2
+\advance\rail@y by -\rail@boxhht
+\rail@put{\makebox(\number\rail@tmpa,\number\rail@boxht){\box\rail@box}}
+\advance\rail@y by \rail@boxhht
+\advance\rail@x by \rail@tmpb
+\rail@put{\oval(\number\rail@tmpa,\number\rail@boxht)}
+\advance\rail@x by \rail@tmpb
+\rail@ex=\rail@x
+\advance\rail@x by \rail@boxrt
+}
+
+\def\rail@coval{
+\rail@tmpb=\rail@tmpa
+\advance\rail@tmpb by \rail@ovalsp
+\ifnum\rail@tmpb<\rail@boxht\rail@tmpb=\rail@boxht\fi
+\advance\rail@tmpb by \rail@boxlf
+\advance\rail@tmpb by \rail@boxrt
+\rail@tmpc=\rail@mx
+\advance\rail@tmpc by -\rail@x
+\advance\rail@tmpc by -\rail@tmpb
+\divide\rail@tmpc by 2
+\ifnum\rail@tmpc>0
+\advance\rail@x by \rail@tmpc
+\fi
+\rail@oval
+}
+
+\def\rail@frame{
+\advance\rail@x by \rail@boxlf
+\rail@eline
+\advance\rail@tmpa by \rail@framesp
+\ifnum\rail@tmpa<\rail@boxht\rail@tmpa=\rail@boxht\fi
+\advance\rail@y by -\rail@boxhht
+\rail@put{\framebox(\number\rail@tmpa,\number\rail@boxht){\box\rail@box}}
+\advance\rail@y by \rail@boxhht
+\advance\rail@x by \rail@tmpa
+\rail@ex=\rail@x
+\advance\rail@x by \rail@boxrt
+}
+
+\def\rail@cframe{
+\rail@tmpb=\rail@tmpa
+\advance\rail@tmpb by \rail@framesp
+\ifnum\rail@tmpb<\rail@boxht\rail@tmpb=\rail@boxht\fi
+\advance\rail@tmpb by \rail@boxlf
+\advance\rail@tmpb by \rail@boxrt
+\rail@tmpc=\rail@mx
+\advance\rail@tmpc by -\rail@x
+\advance\rail@tmpc by -\rail@tmpb
+\divide\rail@tmpc by 2
+\ifnum\rail@tmpc>0
+\advance\rail@x by \rail@tmpc
+\fi
+\rail@frame
+}
+
+\def\rail@text{
+\advance\rail@x by \rail@textlf
+\advance\rail@y by \rail@textup
+\rail@put{\box\rail@box}
+\advance\rail@y by -\rail@textup
+\advance\rail@x by \rail@tmpa
+\advance\rail@x by \rail@textrt
+}
+
+% alternatives
+%
+% \rail@jx \rail@jy : current join point
+%
+% \rail@gx \rail@gy \rail@gex \rail@grx : global versions of \rail@x etc,
+%                                         to pass values over group closings
+%
+% \rail@mx : maximum x so far
+%
+% \rail@sy : starting \rail@y for alternatives
+%
+% \rail@jput : put at (\rail@jx,\rail@jy)
+%
+% \rail@joval[PART] : put \oval[PART] with adjust
+
+\newcount\rail@jx
+\newcount\rail@jy
+
+\newcount\rail@gx
+\newcount\rail@gy
+\newcount\rail@gex
+\newcount\rail@grx
+
+\newcount\rail@sy
+\newcount\rail@mx
+
+\def\rail@jput{
+\put(\number\rail@jx,\number\rail@jy)
+}
+
+\def\rail@joval[#1]{
+\advance\rail@jx by \rail@joinadj
+\rail@jput{\oval(\number\rail@joinsz,\number\rail@joinsz)[#1]}
+\advance\rail@jx by -\rail@joinadj
+}
+
+% \rail@barsplit : incoming split for '|'
+%
+% \rail@plussplit : incoming split for '+'
+%
+
+\def\rail@barsplit{
+\advance\rail@jy by -\rail@joinhsz
+\rail@joval[tr]
+\advance\rail@jx by \rail@joinhsz
+}
+
+\def\rail@plussplit{
+\advance\rail@jy by -\rail@joinhsz
+\advance\rail@jx by \rail@joinsz
+\rail@joval[tl]
+\advance\rail@jx by -\rail@joinhsz
+}
+
+% \rail@alt{SPLIT} : start alternatives with incoming split SPLIT
+%
+
+\def\rail@alt#1{
+\rail@sy=\rail@y
+\rail@jx=\rail@x
+\rail@jy=\rail@y
+\advance\rail@x by \rail@joinsz
+\rail@mx=0
+\let\rail@list=\@empty
+\let\rail@comma=\@empty
+\let\rail@split=#1
+\begingroup
+\rail@sx=\rail@x
+\rail@rx=0
+}
+
+% \rail@nextalt{FIX}{Y} : start next alternative at vertical position Y
+%                         and fix-up FIX
+%
+
+\def\rail@nextalt#1#2{
+\global\rail@gx=\rail@x
+\global\rail@gy=\rail@y
+\global\rail@gex=\rail@ex
+\global\rail@grx=\rail@rx
+\endgroup
+#1
+\ifnum\rail@gx>\rail@mx\rail@mx=\rail@gx\fi
+\ifnum\rail@grx>\rail@mx\rail@mx=\rail@grx\fi
+\edef\rail@list{\rail@list\rail@comma\number\rail@gex:\number\rail@gy}
+\def\rail@comma{,}
+\rail@split
+\let\rail@split=\@empty
+\rail@sety{#2}
+\rail@tmpa=\rail@jy
+\advance\rail@tmpa by -\rail@y
+\advance\rail@tmpa by -\rail@joinhsz
+\rail@jput{\line(0,-1){\number\rail@tmpa}}
+\rail@jy=\rail@y
+\advance\rail@jy by \rail@joinhsz
+\advance\rail@jx by \rail@joinhsz
+\rail@joval[bl]
+\advance\rail@jx by -\rail@joinhsz
+\rail@ex=\rail@x
+\begingroup
+\rail@sx=\rail@x
+\rail@rx=0
+}
+
+% \rail@barjoin : outgoing join for first '|' alternative
+%
+% \rail@plusjoin : outgoing join for first '+' alternative
+%
+% \rail@altjoin : join for subsequent alternative
+%
+
+\def\rail@barjoin{
+\ifnum\rail@y<\rail@sy
+\global\rail@gex=\rail@jx
+\else
+\global\rail@gex=\rail@ex
+\fi
+\advance\rail@jy by -\rail@joinhsz
+\rail@joval[tl]
+\advance\rail@jx by -\rail@joinhsz
+\ifnum\rail@y<\rail@sy
+\rail@altjoin
+\fi
+}
+
+\def\rail@plusjoin{
+\global\rail@gex=\rail@ex
+\advance\rail@jy by -\rail@joinhsz
+\advance\rail@jx by -\rail@joinsz
+\rail@joval[tr]
+\advance\rail@jx by \rail@joinhsz
+}
+
+\def\rail@altjoin{
+\rail@eline
+\rail@tmpa=\rail@jy
+\advance\rail@tmpa by -\rail@y
+\advance\rail@tmpa by -\rail@joinhsz
+\rail@jput{\line(0,-1){\number\rail@tmpa}}
+\rail@jy=\rail@y
+\advance\rail@jy by \rail@joinhsz
+\advance\rail@jx by -\rail@joinhsz
+\rail@joval[br]
+\advance\rail@jx by \rail@joinhsz
+}
+
+% \rail@eltsplit EX:Y; : split EX:Y into \rail@ex \rail@y
+%
+% \rail@endalt{JOIN} : end alternatives with outgoing join JOIN
+
+\def\rail@eltsplit#1:#2;{\rail@ex=#1\rail@y=#2}
+
+\def\rail@endalt#1{
+\global\rail@gx=\rail@x
+\global\rail@gy=\rail@y
+\global\rail@gex=\rail@ex
+\global\rail@grx=\rail@rx
+\endgroup
+\ifnum\rail@gx>\rail@mx\rail@mx=\rail@gx\fi
+\ifnum\rail@grx>\rail@mx\rail@mx=\rail@grx\fi
+\edef\rail@list{\rail@list\rail@comma\number\rail@gex:\number\rail@gy}
+\rail@x=\rail@mx
+\rail@jx=\rail@x
+\rail@jy=\rail@sy
+\advance\rail@jx by \rail@joinsz
+\let\rail@join=#1
+\@for\rail@elt:=\rail@list\do{
+\expandafter\rail@eltsplit\rail@elt;
+\rail@join
+\let\rail@join=\rail@altjoin
+}
+\rail@x=\rail@mx
+\rail@y=\rail@sy
+\rail@ex=\rail@gex
+\advance\rail@x by \rail@joinsz
+}
+
+% \rail@bar : start '|' alternatives
+%
+% \rail@nextbar : next '|' alternative
+%
+% \rail@endbar : end '|' alternatives
+%
+
+\def\rail@bar{
+\rail@alt\rail@barsplit
+}
+
+\def\rail@nextbar{
+\rail@nextalt\relax
+}
+
+\def\rail@endbar{
+\rail@endalt\rail@barjoin
+}
+
+% \rail@plus : start '+' alternatives
+%
+% \rail@nextplus: next '+' alternative
+%
+% \rail@endplus : end '+' alternatives
+%
+
+\def\rail@plus{
+\rail@alt\rail@plussplit
+}
+
+\def\rail@nextplus{
+\rail@nextalt\rail@fixplus
+}
+
+\def\rail@fixplus{
+\ifnum\rail@gy<\rail@sy
+\begingroup
+\rail@x=\rail@gx
+\rail@y=\rail@gy
+\rail@ex=\rail@gex
+\rail@rx=\rail@grx
+\ifnum\rail@x<\rail@rx
+\rail@x=\rail@rx
+\fi
+\rail@eline
+\rail@jx=\rail@x
+\rail@jy=\rail@y
+\advance\rail@jy by \rail@joinhsz
+\rail@joval[br]
+\advance\rail@jx by \rail@joinhsz
+\rail@tmpa=\rail@sy
+\advance\rail@tmpa by -\rail@joinhsz
+\advance\rail@tmpa by -\rail@jy
+\rail@jput{\line(0,1){\number\rail@tmpa}}
+\rail@jy=\rail@sy
+\advance\rail@jy by -\rail@joinhsz
+\advance\rail@jx by \rail@joinhsz
+\rail@joval[tl]
+\advance\rail@jy by \rail@joinhsz
+\global\rail@gx=\rail@jx
+\global\rail@gy=\rail@jy
+\global\rail@gex=\rail@gx
+\global\rail@grx=\rail@rx
+\endgroup
+\fi
+}
+
+\def\rail@endplus{
+\rail@endalt\rail@plusjoin
+}
+
+% \rail@cr{Y} : carriage return to vertical position Y
+
+\def\rail@cr#1{
+\rail@tmpa=\rail@sx
+\advance\rail@tmpa by \rail@joinsz
+\ifnum\rail@x<\rail@tmpa\rail@x=\rail@tmpa\fi
+\rail@eline
+\rail@jx=\rail@x
+\rail@jy=\rail@y
+\advance\rail@x by \rail@joinsz
+\ifnum\rail@x>\rail@rx\rail@rx=\rail@x\fi
+\advance\rail@jy by -\rail@joinhsz
+\rail@joval[tr]
+\advance\rail@jx by \rail@joinhsz
+\rail@sety{#1}
+\rail@tmpa=\rail@jy
+\advance\rail@tmpa by -\rail@y
+\advance\rail@tmpa by -\rail@boxsp
+\advance\rail@tmpa by -\rail@joinhsz
+\rail@jput{\line(0,-1){\number\rail@tmpa}}
+\rail@jy=\rail@y
+\advance\rail@jy by \rail@boxsp
+\advance\rail@jy by \rail@joinhsz
+\advance\rail@jx by -\rail@joinhsz
+\rail@joval[br]
+\advance\rail@jy by -\rail@joinhsz
+\rail@tmpa=\rail@jx
+\advance\rail@tmpa by -\rail@sx
+\advance\rail@tmpa by -\rail@joinhsz
+\rail@jput{\line(-1,0){\number\rail@tmpa}}
+\rail@jx=\rail@sx
+\advance\rail@jx by \rail@joinhsz
+\advance\rail@jy by -\rail@joinhsz
+\rail@joval[tl]
+\advance\rail@jx by -\rail@joinhsz
+\rail@tmpa=\rail@boxsp
+\advance\rail@tmpa by -\rail@joinsz
+\rail@jput{\line(0,-1){\number\rail@tmpa}}
+\advance\rail@jy by -\rail@tmpa
+\advance\rail@jx by \rail@joinhsz
+\rail@joval[bl]
+\rail@x=\rail@jx
+\rail@ex=\rail@x
+}