\documentclass[12pt]{article}
 \input diagxy
 \textwidth 6in
 \oddsidemargin 0pt
 \makeindex
\begin{document}
\def\xypic{\hbox{\rm\Xy-pic}}

\title{A new diagram package (Version \thedate)}
\author{Michael Barr\\Dept of Math and Stats, McGill University
\\barr@barrs.org}
 \date{}
 \maketitle
\tableofcontents


\kern 40pt
{\narrower
For the fashion of Minas Tirith was such that it was built on seven levels,
each delved into a hill, and about each was set a wall, and in each wall
was a gate.

-- J.R.R.\ Tolkien, ``The Return of the King''\footnote{These macros are
at the seventh level of nesting.  The first level is the code actually
executed directly by the processor.  The second is the microcode, burned
into the chip, that interprets the assembly language instructions into
the ones that are directly executed.  Level three is the language,
usually C, but originally Pascal, into which the Web code, the fourth
level, is compiled.  The fifth level is \TeX\ itself, which is best seen
as a high level programming language for mathematical text processing.
Level six is the \xypic\ code in which these macros, level seven, are
written.}

}


\kern 5pt
 Note:  This is the first increase in functionality in a couple years.
Following a suggestion of Gerd Zeibig (who implemented this in a very
different way), I have added a new feature wherein you can create simple
identifiers for nodes and then describe arrows between those nodes using
the identifiers.  See~\ref{nodes&arrows} for details, syntax and
examples.  I have also recently added support for loops, both inline and
in diagrams.

Note (2008-01-21): The main thing that is changed is in the arrow
specification `.$>$'.  What the standard package produces are very fine
dots.  They are actually tiny rules, about .4 pt square.  I have changed
them to being about .7 pt square, which makes them more visible.  In
addition, there is a newdir {d}, used as `{}{d}$>$' (otherwise the {d}
gets treated as a tail, not a shaft) that substitutes . for those tiny
rules.  The only problem is it works well only for arrows that are
horizontal or nearly so (up to about 30 degrees).  I played with many
variations of the definition, but could not make any of them work right.
In principle, I would prefer to get this right, but several hours of
playing with it did not succeed in solving the `Whack-a-Mole' problem.
If it looked good at some angles, it was worse at others.  I could get
them looking good for both horizontal and vertical arrows, but then the
45 degree ones looked awful.  Aside from that there are some minor bug
fixes.

Note (2008-12-02) What has been added are new macros \verb+\Diamond+,
\verb+\rlimto+, and \verb+\llimto+.  \verb+\Diamond+ is capitalized to
avoid clashing with a standard macro \verb+\diamond+.  It has the same
paramter sets as \verb+\square+.  The other two have no parameters and
are only for the purpose of putting a right, resp. left, arrow to the
right of or under \verb+\lim+.  They will go under in a display or if
you follow \verb+\lim+ by \verb+\limits+.

\section{Why another diagram package?}

This started when a user of my old package, diagram, wrote to ask me if
dashed lines were possible.  The old package had dashed lines for
horizontal and vertical arrows, but not any other direction.  The reason
for this was that \LaTeX\ used rules for horizontal and vertical arrows,
but had its own fonts for other directions.  While rules could be made
any size, the smallest lines in other directions were too long for
decent looking dashes.  Presumably, Lamport was worried about compile
time and file size if the lines were too short, considerations that have
diminished over the years since.  Also arrows could be drawn in only 48
different directions, which is limiting.  My macros were not very well
implemented for slopes like 4 and 1/4, since I never used such lines.

There was certainly an alternative, \xypic, for those who wanted
something better.  But it was hard to learn and I was not entirely happy
with the results.  The basic interface used an
\index{\backslash halign}\verb.\halign..  This
meant that no extra space was allotted to an arrow that had a large
label.  In addition, the different slots could have different horizontal
size, which could result in a misshapen diagram.  I used it in a paper
that had a `W' shaped diagram whose nodes had different widths and the
result was quite obviously misshapen.  On the other hand, the graphics
engine underlying \xypic\ is really quite remarkable and it occurred to
me that I could try to redraft diagram as a front end.  The result is
the current package.  It has been tested mainly with version 3.7, so
there is no guarantee it would work with any earlier version (or, for
that matter, later).  A limited amount of testing with version 3.6
suggests that the only thing that does not work is the 2-arrows; these
come out vanishingly short.

So despite the desire for logical programming, it still seems that for
some purposes, it is desirable to have a system in which you specify
what goes where and where the arrows are drawn.

\subsection{The latest version}
The latest version can be downloaded at
\verb,ftp://ftp.math.mcgill.ca/pub/barr/diagxy.zip, or by anonymous ftp
from \verb,ftp.math.mcgill.ca//pub/barr/diagxy.zip,.


\subsection{Main features}

\begin{itemize}
 \item A general arrow drawing function
\index{\backslash morphism}\verb.\morphism..
 \item Various common diagram shapes such as squares, triangles, etc.
 \item A few special shapes such as cube and $3\times3$ diagrams.
 \item Small 2-arrows that can be placed anywhere in a diagram, much
like \LaTeX's
picture
 environment.
 \item A uniform syntax, while allowing access to all of \xypic's
capabilities
 \item Never expires and does not request acknowledgment.
\end{itemize}

\subsection{Compatibility}
The syntax described below is not compatible with the original diagram
package.  Every front end of this sort represents a trade-off between
simplicity and utility.  A package that simply upgraded the syntax to
allow more dashed (and dotted) lines would have been just as easy to
implement, but would have made poor use of the wonderful possibilities
of the underlying \xypic\ package.  Also there would have been too many
different arrow specifications (they would have had to go at least in
the range $[-9,9]$) for easy memory) and still would not have included
things like inclusion arrows.  To those who would have liked a simpler
syntax, I apologize.  Those who would want more flexibility, I remind
that the entire \xypic\ package is there for use.

\subsection{Errant spaces}
 There is one point that cannot be made too strongly.  {\em Watch for
errant spaces.} Unlike the old diagram package, which was carried out in
math mode so that spaces were ignored, \xypic\ is not in math mode and
spaces will mess up your diagrams.  On the other hand, it will not be
necessary to enclose duplicate nodes inside
\index{\backslash phantom}\verb.\phantom., since the
registration between different nodes is perfect.  In the old package,
for reasons that I now understand, objects did not always register
properly.  This was a flaw built in to the very heart of the package and
is not worth correcting, although it could have been done better in the
first place.  If you see an object in double vision, then the almost
certain cause is that a space has gotten in there somewhere.  I have
attempted to prevent this by liberal use of
\index{\backslash ignorespaces}\verb.\ignorespaces.  in the
definitions, but one cannot always be sure and while testing, I found a
number seemingly innocuous spaces that messed up diagrams.  When in
doubt, always terminate a specification with a
\index{%}\verb.%..  See the
examples.

\subsection{Font sizes}
 According to the documentation of \xypic, the declarations
\begin{verbatim}
\xyoption{tips}
\SelectTips{xy}{12}
\end{verbatim}
 \index{tips} will cause 12 point tips to be used.  This does not appear
to be the case.  The only way I can seem to get larger font sizes is to
add \index{\backslash fontscale{x}}\verb.\fontscale{x}., with \index{x}\verb.x.
taking on the values \verb.0,h,1,2,3,4,5., after \xypic\ is loaded.
With \verb.11pt. you will want \verb.h. and with \verb.12pt. you will
want 1. The others are in case you use larger sizes for transparencies
or for later reduction, in conjunction with extarticle.cls.  While on
the subject, I might mention that if
you want thicker arrow shafts without enlarging anything else you could
add the declaration
\begin{verbatim}
\font\xydashfont=xydash scaled \magstep1
\end{verbatim}
or even larger.  However, this does not thicken the arrow tips and is
not really recommended.  There is probably no way (short of creating
your own fonts) to thicken the tips without also lengthening them.

I had some trouble generating the font files at the larger sizes, so the
file xyfonts.zip, found at my ftp site (ftp.math.mcgill.ca/pub/barr) has
fonts for the ljfour generated at all sizes from 10--20 points.

\subsection{Acknowledgments}
 First, I would like to thank Kris Rose for a superb programming job
that made this package possible.  The original versions of \xypic\ were
based on matrices, but this version includes code to place an arrow with
two nodes (more precisely, their centers) a user-definable distance
apart and that is exactly what I needed.  Second I would like to thank
Ross Moore who answered innumerable questions about the use of the
macros that the documentation did not answer or at least I could not
understand what it said.  I thank Donald Arsenau answered several of my
questions about the internals of \TeX\ that I did not understand
clearly and Steve Bloom who found a couple
of typos in the first version of these notes.  Finally, I would like to
thank all those, but especially Charles Wells, who gave me opinions on
the best syntax.  But I made the final decisions and if you have any
complaints, you can direct them to me.  Not that I am likely to change
anything at this date.

\subsection{License}
 The use of this package is unrestricted.  It may be freely distributed,
unchanged, for non-commercial or commercial use.  If changed, it must be
renamed.  Inclusion in a commercial software package is also permitted,
but I would appreciate receiving a free copy for my personal examination
and use.  There are no guarantees that this package is good for
anything.  I have tested it with LaTeX 2e, LaTeX 2.09 and Plain TeX.
Although I know of no reason it will not work with AMSTeX, I have not
tested it.

\section{The basic syntax}

The basic syntax is built around an operation
\index{\backslash morphism}\verb.\morphism.  that is
used as \index{\backslash morphism}
 \begin{verbatim}
 \morphism(x,y)|p|/{sh}/<dx,dy>[N`N;L]
 \end{verbatim}
 The last group of parameters is required.  They are the source and
target nodes of the arrow and the label.  The remaining parameters are
optional and default to commonly used values.  Currently, the
\verb.L.\index{label} is set in \index{\backslash scriptstyle}\verb.\scriptstyle.
size, but this can easily be changed by putting
\index{\backslash let\backslash labelstyle=\backslash textstyle}
\verb.\let\labelstyle=\textstyle. in
your file.

 The parameters \verb.x. and \verb.y. give the location of the source
node within a fixed local coordinate system and \verb-x+dx- and
\verb-y+dy- locate the target.  To be precise, the first coordinate is
the horizontal center of the node and the second is that of the base
line.  These distances are given in terms of \index{\backslash ul}\verb.\ul.'s,
(for unitlength), which is user assignable, but currectly is .01em.  The
placement parameter \verb.p. is one of \verb.a,b,l,r,m. that stand for
above, below, left, right, or mid and describe the positioning of the
arrow label on the arrow.  If it is given any value other than those
five, it is ignored.  We describe below why you might want it ignored.
The label \index{m}\verb.m. stands for a label positioned in the middle
of a split arrow.  When used on a non-vertical arrow, \index{a}\verb.a.
positions the label above the arrow and \index{b}\verb.b. positions it
below.  On a vertical arrow, the positioning depends on whether the
arrow points up or down.  Similarly, when used on a non-horizontal
arrow, \index{l}\verb.l. positions the label to the left and
\index{r}\verb.r. positions it to the right, while on a horizontal arrow
it depends on which way it points.

The shape parameter \verb.sh. describes the shape of the arrow.  An
arrow is thought of as consisting of three parts, the tail, the shaft
and the head.  You may specify just the head, in which case the shaft
will be an ordinary line, or all three.  However, since the tail can be
(and usually is) empty, in practice you can also describe the shaft and
tail.  In addition, it is possible to modify the arrow in various ways.
Although the parameter is shown within braces, the braces can be omitted
unless one of the modifier characters is \verb./., in which case, {\em
the entire parameter} must be put in braces.  It is important to note
that it will not work just to put the \verb./. inside the braces, since
this will interfere with the internal parsing of \xypic.  The head and
tail shapes are basically one of \index{>}\verb.>., \index{>>}\verb.>>.,
\verb.(., \verb.)., \index{>}\verb*+>+, and \index{<}\verb*+<+.  Each of
these may also be preceded by \index{^}\verb.^. or \index{_}\verb._. and
others are user definable.  For details, see the \xypic\ reference
manual.  The first of these is an ordinary head, while the second is for
an epic arrow.  The third is not much used, but the superscripted
version makes and inclusion tail, as will be illustrated below.  The
reverse ones give reversed arrowheads.  The sign \verb*+ + stands for an
obligatory space and it leaves extra space for a tailed (monic) arrow,
which otherwise runs into the source node.  Although there are many
possibilities for shafts, including alphanumeric characters, the ones
that mainly interest us are:  \index{-}\verb.-., which is an ordinary
shaft, \index{--}\verb.--., which produces a dashed arrow,
\index{=}\verb.=., which gives a double arrow (although with only one
arrowhead), and ., which makes a dotted arrow.  Thus \index{>}\verb.>.
or \index{->}\verb.->. will produce an ordinary arrow,
\index{->>}\verb.->>. an epic arrow, \index{ >->}\verb*+ >->+ makes a
monic arrow, and \index{-->>}\verb.-->>. would make a dashed epic arrow.
The descriptions \index{<-}\index{<<-}\verb.<-,<<-,.  \index{<-<
}\verb*+<-< +, and \index{<<--}\verb.<<--. give the reversed versions.
Note that \index{<}\verb.<. does not give a reversed arrow, since
\xypic\ interprets that as a reversed head, not a tail.

If the shape parameter begins with an \index{@}\verb.@., it is
interpreted differently.  In that case, it has the form
\index{@{shape}@}\verb.@{shape}@. modifier, where the modifier is as
described in the \xypic\ reference guide.  I just mention a couple of
them.  The parameter \index{@{->}@<3pt>}\verb.@{->}@<3pt>., for example,
would give an ordinary arrow moved three points in the direction
perpendicular to that of the arrow.  If you give
\index{{@{->>}@/^5pt/}}\verb.{@{->>}@/^5pt/}., you will get an epic
arrow that is curved in the direction perpendicular to the direction of
the arrow by five points.  It is imperative that a specification such as
\index{@{>}@/5pt/}\verb.@{>}@/5pt/. be enclosed in braces because of the
\index{/}\verb./.s.

\subsection{A word about parameters}
 I have already mentioned the necessity of enclosing certain arrow shape
specifications in braces.  Because of the way \TeX\ operates, I have
used a number of different delimiters:  \index{(}\verb.(.,
\index{)}\verb.)., \index{|}\verb.|., \index{/}\verb./.,
\index{<}\verb.<., \index{>}\verb.>., \index{[}\verb.[.,
\index{]}\verb.]., \index{`}\verb.`., and \index{;}\verb.;..  Any of
these that appear inside an argument could conceivably cause problems.
They were chosen as the least likely to appear inside mathematics
(except for \index{(,)}\verb.(,). which appear in positions that are
unlikely to cause problems).  However, be warned that this is a possible
cause of mysterious error messages.  If this happens, enclosing the
offending parameter in braces should cure the problem.  The exceptions
come when the braces interfere with \xypic's somewhat arcane parsing
mechanism.  One place it imperative to use braces is if you attempt to
use a disk as a tip.  Although most tips do not have to be enclosed in
braces, you get a small solid disk tip from \index{{*}}\verb.{*}. and
not from \index{*}\verb.*.  (see the note at the bottom of the first
column of page 42 in the reference manual.  The first three of
\begin{verbatim}
\morphism(0,300)|a|/-*/<500,0>[A`B;f]
\morphism(0,0)|a|/{-*}/<500,0>[A`B;f]
\morphism(0,0)|a|/{*}/<500,0>[A`B;f]
\morphism(0,0)|a|/-{*}/<500,0>[A`B;f]
\end{verbatim}
 give error messages.  Only the fourth works:
 $$\bfig
\morphism(0,0)|a|/-{*}/<500,0>[A`B;f]
 \efig$$

In addition to the diagrams, there are macros that are intended to be
used inline to make horizontal arrows, pointing left or right, plain,
monic, epic, or user-definable shapes, and calculating their own length
to fit the label.  Finally, there is a macro for making short 2-arrows
that may be placed (actually, \index{\backslash place}\verb.\place.d) anywhere in
a diagram.


\section{Defined diagrams}

Using the basic
\index{\backslash morphism}\verb.\morphism.  macro, I have a defined a number of
diagrams:  squares (really rectangles) and variously oriented triangles
and a few compound diagrams.  The basic shapes are exactly the same as
in the old diagram package, but the options are done entirely
differently.  Here is the syntax of the
\index{\backslash square}\verb.\square.  macro:
 \begin{verbatim}
 \square(x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dx,dy>[N`N`N`N;L`L`L`L]
 \end{verbatim}
 Each of the first four sets of parameters is optional and any subset of
them can be omitted.  (Note that only the sets can be omitted, once you
give \index{dx}\verb.dx., you also have to give \index{dy}\verb.dy. and
so on.)  The first set gives the horizontal and vertical position (in a
local coordinate system) of the lower left corner of the square, the
next four give the label placements using the same five characters
previously described.  The next four give the shapes of the arrows using
the same syntax as discussed above.  The last group is horizontal and
vertical size of the square.  More precisely, the \index{x}\verb.x.
coordinate is that of the midpoint of the node, while the
\index{y}\verb.y. coordinate is that of the baseline of the node.  This
is entirely based on \xypic.

In the case of other shapes, discussed below, the positioning parameter
may be different.  The \index{x}\verb.x. coordinate is the midpoint of
the leftmost node and the \index{y}\verb.y. coordinate is the baseline
of the lowest node.  In the case of the
\index{\backslash qtriangle}\verb.\qtriangle.,
\index{\backslash Vtriangle}\verb.\Vtriangle., and
\index{\backslash Ctriangle}\verb.\Ctriangle. described below, these are different
nodes.  What this positioning means is that if you specify the
coordinates and sizes correctly the shapes will automatically fit
together.  The last example on Page~\pageref{TTTdiag} illustrates this.

Here is a listing of the shapes, together with the groups of parameters.
In all cases, the first four groups are optional and any subset of them
will work.  However, they must come in the order given.  Note that the
names of the triangles are related to the shape as the shape that best
approximates the shape of the letter.  For example, a
\index{\backslash ptriangle}\verb.\ptriangle. is a right triangle that has its
hypotenuse going from upper right to lower left.  Triangles with lower
case names have their legs horizontal and vertical and the dimension
parameters are the lengths of the legs.  Those with capitalized names
have their hypotenuse horizontal or vertical.  In those cases, one of
\index{dx}\verb.dx. or \index{dy}\verb.dy. is the length of a leg and
the other is {\em half} the length of the hypotenuse.  In all cases, the
order of the nodes and of the arrows is linguistic, first moving from
left to right and then down.  The defaults are reasonable, but with
triangles, there is not always a natural direction for arrows.  I always
made mistakes in the order with my macros and this is certainly a
defect.  But the order is the same.  In every case the braces around the
shape specification can be removed unless it includes the following
delimiter (that is, \index{`}\verb.`. or \index{/}\verb./., as the case
may be.)
 \begin{verbatim}
\square(x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dx,dy>%
 [N`N`N`N;L`L`L`L]
\ptriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\qtriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\dtriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\btriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\Atriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\Vtriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\Ctriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\Dtriangle(x,y)|ppp|/{sh}`{sh}`{sh}/<dx,dy>[N`N`N;L`L`L]
\Atrianglepair(x,y)|ppppp|/{sh}`{sh}`{sh}`{sh}`{sh}/%
<dx,dy>[N`N`N`N;L`L`L`L`L]
\Vtrianglepair(x,y)|ppppp|/{sh}`{sh}`{sh}`{sh}`{sh}/%
<dx,dy>[N`N`N`N;L`L`L`L`L]
\Ctrianglepair(x,y)|ppppp|/{sh}`{sh}`{sh}`{sh}`{sh}/%
<dx,dy>[N`N`N`N;L`L`L`L`L]
\Dtrianglepair(x,y)|ppppp|/{sh}`{sh}`{sh}`{sh}`{sh}/%
<dx,dy>[N`N`N`N;L`L`L`L`L]
\end{verbatim}
 \index{\backslash square} \index{\backslash ptriangle} \index{\backslash qtriangle} \index{\backslash dtriangle}
\index{\backslash btriangle} \index{\backslash Atriangle} \index{\backslash Vtriangle}
\index{\backslash Ctriangle} \index{\backslash Dtriangle} \index{\backslash Atrianglepair}
\index{\backslash Vtrianglepair} \index{\backslash Ctrianglepair} \index{\backslash Dtrianglepair}
Note that the
\verb.%.  signs are required if you break the
macro at such points.  See also the discussion of errant spaces above.

To make a diagram, you have to enclose it inside \index{\backslash xy ...
\backslash endxy}.\verb,\xy ...  \endxy,.  You will usually want it
displayed,
for which the simplest way is to enclose it in \index{$$\xy ...
\endxy$$}\verb,$$\xy...\endxy$$,.  In previous versions of this, the
macros
\index{\backslash bfig}\verb.\bfig. and \index{\backslash efig}\verb.\efig. be synonyms for
 were synonyms for
\index{\backslash xy}\verb.\xy. and \index{\backslash endxy}\verb.\endxy.,
resp.  They have now been redefined to also put the box produced by
\verb.\xy. into a \verb.\vcenter. box.  The effect of this is that when
\index{\backslash eqno}\verb.\eqno. is used with a diagram, the
resulting equation number will be vertically centered.


\section{Examples}

Many people---including me---learn mainly by example and
I will give a number of examples here.  The formal
syntax that is not given here can be learned in the \xypic\ reference
manual. More samples from an actual paper can be found in
\verb,ftp.math.mcgill.ca/pub/barr/derfun.tex,.  If you want to compile
that paper, you will need \verb,tac.cls,, available from \verb,tac.ca,.
We begin with \index{\backslash morphism}
\begin{verbatim}
 $$\bfig
 \morphism[A`B;f]
 \morphism(0,300)[A`B;f]
 \morphism(0,600)|m|[A`B;f]
 \morphism(0,900)/<-/[A`B;f]
 \morphism(900,500)<0,-500>[A`B;f]
 \morphism(1200,0)<0,500>[A`B;f]
 \efig$$
\end{verbatim}
which gives the diagram
 $$\bfig
 \morphism[A`B;f]
 \morphism(0,300)[A`B;f]
 \morphism(0,600)|m|[A`B;f]
 \morphism(0,900)/<-/[A`B;f]
 \morphism(900,500)<0,-500>[A`B;f]
 \morphism(1200,0)<0,500>[A`B;f]
 \efig$$
\begin{verbatim}
 $$\bfig
\square[A`B`C`D;e`f`g`m]
 \efig$$
\end{verbatim}
 produces
 $$\bfig
\square[A`B`C`D;e`f`g`m]
 \efig$$
 This can be modified, for example
\begin{verbatim}
 $$\bfig
\square/>>`>`>` >->/[A`B`C`D;e`f`g`m]
 \efig$$
\end{verbatim}
 produces
 $$\bfig
\square/>>`>`>` >->/[A`B`C`D;e`f`g`m]
 \efig$$
 This can be put together with a morphism as follows:
\begin{verbatim}
 $$\bfig
\square/>>`>`>` >->/[A`B`C`D;e`f`g`m]
 \morphism(500,500)|m|/.>/<-500,-500>[B`C;h]
 \efig$$
\end{verbatim}
 \index{\backslash square}
 which makes a familiar diagram:
 $$\bfig
\square/>>`>`>` >->/[A`B`C`D;e`f`g`m]
 \morphism(500,500)|m|/.>/<-500,-500>[B`C;h]
 \efig$$
 The same diagram could have been made by
\begin{verbatim}
 $$\bfig
 \ptriangle|alm|/>>`>`.>/[A`B`C;e`f`h]
 \dtriangle/`>` >->/[B`C`D;`g`m]
 \efig$$
\end{verbatim}
\index{\backslash ptriangle} \index{\backslash dtriangle}

There are four macros for making pairs of triangles put together:
 $$\bfig
 \Vtrianglepair[A`B`C`D;f`g`h`k`l]
 \efig$$
 comes from
\begin{verbatim}
 $$\bfig
 \Vtrianglepair[A`B`C`D;f`g`h`k`l]
 \efig$$
\end{verbatim}
 \index{\backslash Vtrianglepair}
 \index{\backslash Atrianglepair}
 \index{\backslash Ctrianglepair}
 \index{\backslash Dtrianglepair}

 The other three are called \verb.\Atrianglepair.,
\verb.\Ctrianglepair., and \verb.\Dtrianglepair..

 You can fit two squares together, horizontally:
\begin{verbatim}
 $$\bfig
\square|almb|[A`B`C`D;f`g`h`k]
\square(500,0)/>``>`>/[B`E`D`F;l``m`n]
 \efig$$
\end{verbatim}
 $$\bfig
\square|almb|[A`B`C`D;f`g`h`k]
\square(500,0)/>``>`>/[B`E`D`F;l``m`n]
 \efig$$
 or vertically
\begin{verbatim}
 $$\bfig
\square(0,500)|alrm|[A`B`C`D;f`g`h`k]
\square/`>`>`>/[C`D`E`F;`l`m`n]
 \efig$$
\end{verbatim}
 $$\bfig
\square(0,500)|alrm|[A`B`C`D;f`g`h`k]
\square/`>`>`>/[C`D`E`F;`l`m`n]
 \efig$$
or a square and a triangle
\begin{verbatim}
 $$\bfig
\Ctriangle/<-`>`>/<400,400>[\hbox{\rm rec}(A,B)`B`X;r_0(A,B)`f`t_0]
 \square(400,0)/<-``>`<-/<1000,800>[\hbox{\rm rec}(A,B)`A\times\hbox{\rm
   rec}(A,B)`X`A\times X;r(A,B)``\hbox{\rm id}_A\times f`t]
 \efig$$
\end{verbatim}
 gives the diagram
 $$\bfig
\Ctriangle/<-`>`>/<400,400>[\hbox{\rm rec}(A,B)`B`X;r_0(A,B)`f`t_0]
 \square(400,0)/<-``>`<-/<1000,800>[\hbox{\rm rec}(A,B)`A\times\hbox{\rm
   rec}(A,B)`X`A\times X;r(A,B)``\hbox{\rm id}_A\times f`t]
 \efig$$
 This diagram is on page 361 of the third edition of Category Theory for
Computing Science to describe recursion.
 Here is an example using the procedure for sliding an arrow sideways.
This one could even be used in a text,
 \index{sliding arrows}
$\xy \morphism(0,0)|a|/@{>}@<3pt>/<400,0>[A`B;d]
\morphism(0,0)|b|/@{>}@<-3pt>/<400,0>[A`B;e]\endxy$
 which was made using
\begin{verbatim}
$\xy \morphism(0,0)|a|/@{>}@<3pt>/<400,0>[A`B;d]
\morphism(0,0)|b|/@{>}@<-3pt>/<400,0>[A`B;e]\endxy$
\end{verbatim}
 Indidentally, if you don't put this in math mode, the diagram will come
out too low, for reasons I do not understand but must be buried within
the \xypic\ code.
Later we will introduce a number of inline procedures.

Something a bit different that illustrates the use of another shaft

\index{=}\verb.=.  that gives a 2-arrow, as well as curved arrows:
\begin{verbatim}
 $$\bfig
\morphism(0,0)|a|/{@{>}@/^1em/}/<500,0>[A`B;f]
\morphism(0,0)|b|/{@{>}@/_1em/}/<500,0>[A`B;g]
\morphism(250,50)|a|/=>/<0,-100>[``]
 \efig$$
\end{verbatim}
 $$\bfig
\morphism(0,0)|a|/{@{>}@/^1em/}/<500,0>[A`B;f]
\morphism(0,0)|b|/{@{>}@/_1em/}/<500,0>[A`B;g]
\morphism(250,50)|a|/=>/<0,-100>[`;]
 \efig$$
 In order to use curved arrows, you must insert
\index{\backslash xyoption{curve}}\verb.\xyoption{curve}.
into your file. Here are two ways of doing three arrows between two
objects, depending on what you like:
\begin{verbatim}
 $$\bfig
 \morphism(0,0)|a|/@{>}@<5pt>/<500,0>[A`B;f]
 \morphism(0,0)|m|/@{>}/<500,0>[A`B;g]
 \morphism(0,0)|b|/@{>}@<-5pt>/<500,0>[A`B;h]
 \efig$$
\end{verbatim}
 which gives
 $$\bfig
 \morphism(0,0)|a|/@{>}@<5pt>/<500,0>[A`B;f]
 \morphism(0,0)|m|/@{>}/<500,0>[A`B;g]
 \morphism(0,0)|b|/@{>}@<-5pt>/<500,0>[A`B;h]
 \efig$$
and
\begin{verbatim}
 $$\bfig
 \morphism(0,0)|a|/{@{>}@/^5pt/}/<500,0>[A`B;f]
 \morphism(0,0)|m|/@{>}/<500,0>[A`B;g]
 \morphism(0,0)|b|/{@{>}@/^-5pt/}/<500,0>[A`B;h]
 \efig$$
\end{verbatim}
 which gives
 $$\bfig
 \morphism(0,0)|a|/{@{>}@/^5pt/}/<500,0>[A`B;f]
 \morphism(0,0)|m|/@{>}/<500,0>[A`B;g]
 \morphism(0,0)|b|/{@{>}@/^-5pt/}/<500,0>[A`B;h]
 \efig$$
 Either of these could also be used inline.

 There is a macro
\index{\backslash place}\verb.\place.
that places that object anywhere.  I have changed the name from
\verb.\put. in order to avoid clashing with the \LaTeX\ picture mode's
\index{\backslash put}\verb.\put..  The syntax is
\verb.\place(x,y)[object]. that places the object at \verb.(x,y)..
There is also an optional parameter that can be used to add any of
\xypic's positioning parameters.  For example
\verb.\place[L](x,y)[object]. will left align the object.  The default
is to center align it.
Here is an example that uses a construction that is undocumented here,
but uses a documented \Xy\ construction:
\begin{verbatim}
\newbox\anglebox
\setbox\anglebox=\hbox{\xy \POS(75,0)\ar@{-} (0,0) \ar@{-} (75,75)\endxy}
 \def\angle{\copy\anglebox}
 $$\bfig
 \square[A`B`C`D;f`g`h`k]
 \place(100,400)[\angle]
 \efig$$
\end{verbatim}
\newbox\anglebox
\setbox\anglebox=\hbox{\xy \POS(75,0)\ar@{-} (0,0) \ar@{-} (75,75)\endxy}
 \def\angle{\copy\anglebox}
 $$\bfig
 \square[A`B`C`D;f`g`h`k]
 \place(100,400)[\angle]
 \efig$$
 Notice that you get a headless arrow by using
\index{\backslash ar@{-}}\verb.\ar@{-}..

Here is a special code installed at the request of Jonathon Funk:
\begin{verbatim}
 $$\bfig
\pullback|brrb|<800,800>[P`X`Y`Z;t`u`v`w]%
|amb|/>`-->`>/<500,500>[A;f`g`h]
 \efig$$
\end{verbatim}
 \index{\backslash pullback}
 $$\bfig
\pullback|brrb|<800,800>[P`X`Y`Z;t`u`v`w]%
|amb|/>`-->`>/<500,500>[A;f`g`h]
 \efig$$
The full syntax for this is
\begin{verbatim}
\pullback(x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dx`dy>[N`N`N`N;L`L`L]%
    |ppp|/{sh}`{sh}`{sh}/<dx,dy>[N;L`L`L]
\end{verbatim}
 Of these only the nodes placed inside brackets are obligatory.  The
first sets of parameters are exactly as for
\index{\backslash square}\verb.\square.  and the
remaining parameters are for the nodes and labels of the outer arrows.
There is no positioning parameters for them; rather you set the
horizontal and vertical separations of the outer node from the square.

Here are some more special constructions.  In general, if you are doing
a square, you should use
\index{\backslash Square}\verb.\Square.  instead of
\index{\backslash square}\verb.\square.
because if figures its own width.  The syntax is almost the same, except
that
\index{dx}\verb.dx.  is omitted.  For example,
\begin{verbatim}
 $$\bfig
 \Square/^{ (}->`>`>`^{ (}->/<350>[{\rm Hom}(A,2^B)`{\rm Sub}(A\times B)`
 {\rm Hom}(A',2^{B'})`{\rm Sub}(A'\times B');\alpha(A,B)```\alpha(A',B')]
 \efig$$
\end{verbatim}
 will produce the square
 $$\bfig
 \Square/^{ (}->`>`>`^{ (}->/<350>[{\rm Hom}(A,2^B)`{\rm Sub}(A\times B)`
 {\rm Hom}(A',2^{B'})`{\rm Sub}(A'\times B');\alpha(A,B)```\alpha(A',B')]
 \efig$$
 There are a couple of points to note here.  Note the use of the
argument
\index{^{ (}->}\verb.^{ (}->.  to get the inclusion arrow.  The
complication is
created by the necessity of adding a bit of extra space before the hook.
You get pretty much the same effect by putting a bit of extra space
after the node:
\begin{verbatim}
 $$\bfig
 \Square/^(->`>`>`^(->/<350>[{\rm Hom}(A,2^B)\,`{\rm Sub}(A\times B)`
 {\rm Hom}(A',2^{B'})\,`{\rm Sub}(A'\times B');\alpha(A,B)```\alpha(A',B')]
 \efig$$
\end{verbatim}
 The full syntax is
\begin{verbatim}
 \Square(x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dy>[N`N`N`N;L`L`L`L]
\end{verbatim}

There are also macros for placing two
\index{\backslash Square}\verb.\Square.s together
horizontally or vertically.  The first is
\index{\backslash hSquares}\verb.\hSquares.  with the
syntax
\begin{verbatim}
\hSquares(x,y)|ppppppp|/{sh}`{sh}`{sh}`{sh}`{sh}`{sh}`{sh}/%
<dy>[N`N`N`N`N`N;L`L`L`L`L`L`L]
\end{verbatim}
The second is
\index{\backslash vSquares}\verb.\vSquares.  with a similar syntex except that there
are two
\index{dy}\verb.dy.  parameters, one for each square:
\begin{verbatim}
\hSquares(x,y)|ppppppp|/{sh}`{sh}`{sh}`{sh}`{sh}`{sh}`{sh}/%
<dy,dy>[N`N`N`N`N`N;L`L`L`L`L`L`L]
\end{verbatim}
 Similarly, there are four macros for making pairs of triangles put
together.  For example,
 $$\bfig
 \Vtrianglepair[A`B`C`D;f`g`h`k`l]
 \efig$$
 comes from
\begin{verbatim}
 $$\bfig
 \Vtrianglepair[A`B`C`D;f`g`h`k`l]
 \efig$$
\end{verbatim}

There is a macro for making cubes\index{\backslash cube}.  The syntax is
\begin{verbatim}
 \cube(x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dx,dy>[N`N`N`N;L`L`L`L]%
      (x,y)|pppp|/{sh}`{sh}`{sh}`{sh}/<dx,dy>[N`N`N`N;L`L`L`L]%
      |pppp|/{sh}`{sh}`{sh}`{sh}/[L`L`L`L]
\end{verbatim}
 The first line of parameters is for the outer square and the second for
the inner square, while the remaining parameters are for the arrows
between the squares.  Only the parameters in square brackets are
required; there are defaults for the others.  Here is an example:
\begin{verbatim}
 $$\bfig
\cube(0,0)|arlb|/ >->` >->`>`>/<1500,1500>[A`B`C`D;f`g`h`k]%
(300,300)|arlb|/>`>`>`>/<400,400>[A'`B'`C'`D';f'`g'`h'`k']%
 |mmmm|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$
\end{verbatim}
 gives the somewhat misshapen diagram
 $$\bfig
\cube(0,0)|arlb|/ >->` >->`>`>/<1500,1500>[A`B`C`D;f`g`h`k]%
(300,300)|arlb|/>`>`>`>/<400,400>[A'`B'`C'`D';f'`g'`h'`k']%
 |mmmm|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$
 because the parameters were oddly chosen.  The defaults center the
squares.  I discovered accidently, while debugging the cube that what I
thought was an out-of-range choice of parameters would produce an offset
cube:
\begin{verbatim}
 $$\bfig
\cube|arlb|/ >->` >->`>`>/<1000,1000>[A`B`C`D;f`g`h`k]%
(400,400)|arlb|/>`>`>`>/<900,900>[A'`B'`C'`D';f'`g'`h'`k']%
 |rrrr|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$
\end{verbatim}
 gives
 $$\bfig
\cube|arlb|/ >->` >->`>`>/<1000,1000>[A`B`C`D;f`g`h`k]%
(400,400)|arlb|/>`>`>`>/<900,900>[A'`B'`C'`D';f'`g'`h'`k']%
 |rrrr|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$


\subsection{Nodes and arrows}\label{nodes&arrows}
Following a suggestion of Gerd Zeibig, who has implemented this in a
very different way, I have added a feature wherein you can specify nodes
and arrows between them.  The nodes can be given simple identifiers and
those used to specify the source and target of the arrows.  The way it
works is that \verb.\node id(x,y)[N]. assigns the node \verb.N. at
position \verb.(x,y). to the identifier \verb.id. which is then used
to refer to that node.  Then \verb.\arrow[id`id;L]. is used to place
arrows at the nodes identified by the identifiers and with label
\verb.L..  There are also optional arguments for label position and
arrowhead shape, so the full macro looks like \verb.|p|/sh/[id`id;L]..
Here is an example.  The code
\begin{verbatim}
$$\bfig
\node a(0,0)[A\otimes B]
\node 3b(700,300)[A'\otimes B']
\node @(0,-500)[A''\otimes B'']
\node xyzzy(500,0)[C\otimes D]
\arrow/->>/[a`3b;f]
\arrow|l|[a`@;g]
\arrow|b|/<-/[xyzzy`@;i\otimes j]
\efig$$
\end{verbatim}
produces the diagram
$$\bfig
\node a(0,0)[A\otimes B]
\node 3b(700,300)[A'\otimes B']
\node @(0,-500)[A''\otimes B'']
\node xyzzy(500,0)[C\otimes D]
\arrow/->>/[a`3b;f]
\arrow|l|[a`@;g]
\arrow|b|/<-/[xyzzy`@;i\otimes j]
\efig$$

Notice, incidentally, that the nodes can be defined either inside or
outside math mode.  If it is done outside, the definitions will persist
(unless redefined) and may be reused.  This is useful when there are two
very similar diagrams.  Also note that the identifiers can be any
string.

An example of a large diagram done this way appears in~

\subsection{Complex diagrams}\label{complex}
In homological algebra one often has a $3\times3$ diagram, with or
without 0's on the margins.  There is a macro to do that:
 \index{3 by 3}\index{\backslash iiixiii}
\begin{verbatim}
 $$\bfig
\iiixiii(0,0)|aammbblmrlmr|/>`>`>`>`>`>`>`>`>`>`>`>/<500,500>{'5436}%
 <400,400>[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
\end{verbatim}
 that gives
 $$\bfig
\iiixiii(0,0)|aammbblmrlmr|/>`>`>`>`>`>`>`>`>`>`>`>/<500,500>{'5436}%
 <400,400>[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
 Here is the explanation.  The arrow parameters are not given in the
usual order, but rather first all the horizontal arrows and then all the
vertical ones, each in their usual order.  The nodes are given in the
usual order.  The fifth parameter is the octal number
\verb.`5436.   (In
\TeX, the
\verb.'.  introduces octal numbers and
\verb.".  introduces
hexadecimal numbers) which corresponds to the binary number
101,100,011,110 that describes the distribution of the 0's around the
margins.  The same results would have been obtained if the number had
been the hexadecimal number
\verb."B1E.  or the decimal number

\verb.2846..  The sixth parameter gives the horizontal and vertical
offset of the 0's, which you often want smaller than the others.  You
must not give the sixth parameter unless you have given a value (which
could be 0) to the fifth or an error condition will result.  Note that
the positioning parameters ignore the 0's so that it is the lower left
node that appears at the position
\verb.(x,y)..  As usual, there are
defaults.
 \begin{verbatim}
 $$\bfig
\iiixiii[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
 $$\bfig
\iiixiii%
 {'5436}[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
 $$\bfig
\iiixiii{'5436}<250,450>[A'`B'`C'`A`B`C`A''`B''`C'';%
f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
\end{verbatim}
 $$\bfig
\iiixiii[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
 $$\bfig
\iiixiii%
 {'5436}[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$
 $$\bfig
\iiixiii{'5436}<250,450>[A'`B'`C'`A`B`C`A''`B''`C'';%
f'`g'`f`g`f''`g''`u`v`w`u'`v'`w']
 \efig$$

A similar macro\index{3 by 2}%
\index{\backslash iiixii}\verb.\iiixii.  has been added for a map between exact
sequences, with parameters similar to the above.  An actual example is
\begin{verbatim}
 $$\bfig
 \iiixii|aaaalmr|<1000,800>[H`G`F`H\oplus H_0`G\oplus H_0\oplus F_0`
F\oplus F_0; f`g`\pmatrix{f&0\cr0&1\cr0&0}`\pmatrix{g&0&0\cr0&0&1}`
 \pmatrix{1\cr0}`\pmatrix{1\cr0\cr0}`\pmatrix{1\cr0}]
\efig$$
\end{verbatim}
                which gives
 $$\bfig
 \iiixii|aaaalmr|<1000,800>[H`G`F`H\oplus H_0`G\oplus H_0\oplus F_0`
F\oplus F_0; f`g`\pmatrix{f&0\cr0&1\cr0&0}`\pmatrix{g&0&0\cr0&0&1}`
 \pmatrix{1\cr0}`\pmatrix{1\cr0\cr0}`\pmatrix{1\cr0}]
\efig$$
 The general syntax is
\begin{verbatim}
 \iiixii(x,y)|ppppppp|/1`2`3`4`5`6`7/<dx,dy>{n}<dx'>[...]
\end{verbatim}
 with the usual meaning.  The number n is a number between 0 and 15
(default 15) that specifies whether and where 0's appear (think binary,
with the high bit at the upper left) and dx' specifies the separation of
the zeroes.  You get two squares side by side if both n and dx' are 0.

\subsection{Empty placement and moving labels}
 The label placements within \verb.|p|. is valid only for
\verb.x=a,b,r,l,m..  If you use any other value (or leave it empty) the
label entry is ignored, but you can use any valid \xypic\ label, as
described in Figure 13 of the reference manual.  One place you might
want to use this is for the placement of the labels along an arrow.  In
\xypic\ the default placement of the label is midway between the
midpoints of the nodes.  If the two nodes are of widely different sizes,
this can result in strange placements; therefore I always place them
midway along the arrow.  However, as the following illustrates, this can
be changed.
 \begin{verbatim}
 $$\bfig
\morphism(0,900)||/@{->}^<>(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,600)||/@{->}^<(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,300)||/@{->}^>(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,0)||/@{->}^(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
 \efig$$
\end{verbatim}
 which produces
 $$\bfig
\morphism(0,900)||/@{->}^<>(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,600)||/@{->}^<(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,300)||/@{->}^>(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,0)||/@{->}^(0.7){f}/<800,0>[A^B\times B^C\times C`C;]
 \efig$$
 Here is the explanation.  The label placement argument is empty (it
cannot be omitted) and the arrow entry is empty.  However, placing
\verb.^(0.7){f}. inside the arrow shape places the label $f$ 7/10 of the
way between the nodes.  Unmodified, this places it 7/10 of the way
between the centers of the nodes.  This may be modified by
\index{<}\verb.<., which moves the first (here the left) reference point
to the beginning of the arrow, \index{>}\verb.>. which moves the second
reference point to the end of the arrow, or by both, which moves both
reference points.  In most cases, you will want both.  Incidentally,
\index{-}\verb.-. is a synonym for the sequence
\index{<>(}5).\verb.<>(.5). and that is the default placement in my
package.

Here are some more examples that illustrates the special sequence
\index{\backslash hole}\verb.\hole. used in conjunction with \index{|}\verb.|.
that implements \index{m}\verb.m. as well as the fact that these things
can be stacked.  For more details, I must refer you to the \xypic\
reference manual.
 \begin{verbatim}
 $$\bfig
\morphism(0,600)||/@{->}|-\hole/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,300)||/@{->}|-\hole^<>(.7)f/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,0)||/@{->}|-\hole^<>(.7)f_<>(.3)g/<800,0>[A^B\times
B^C\times C`C;]
 \efig$$
\end{verbatim}
 produces
 $$\bfig
\morphism(0,600)||/@{->}|-\hole/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,300)||/@{->}|-\hole^<>(.7)f/<800,0>[A^B\times B^C\times C`C;]
\morphism(0,0)||/@{->}|-\hole^<>(.7)f_<>(.3)g/<800,0>[A^B\times
B^C\times C`C;]
 \efig$$

Here is another version of the cube we looked at above, using these
special placements and\index{\backslash cube}
\index{\backslash hole}\verb.\hole.'s to break some lines and make it
neater.
\begin{verbatim}
 $$\bfig
\cube|arlb|/@{ >->}^<>(.6){f}` >->`@{>}_<>(.4){h}`>/%
<1000,1000>[A`B`C`D;`g``k]%
(400,400)|axxb|/>`@{>}|!{(300,1000);(500,1000)}\hole^<>(.6){g'}`>`@{>}%
|!{(1000,500);(1000,300)}\hole_<>(.4){k'}/<900,900>[A'`B'`C'`D';f'``h'`]%
 |rrrr|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$
\end{verbatim}
 $$\bfig
\cube|arlb|/@{ >->}^<>(.6){f}` >->`@{>}_<>(.4){h}`>/%
<1000,1000>[A`B`C`D;`g``k]%
(400,400)|axxb|/>`@{>}|!{(300,1000);(500,1000)}\hole^<>(.6){g'}`>`@{>}%
|!{(1000,500);(1000,300)}\hole_<>(.4){k'}/<900,900>[A'`B'`C'`D';f'``h'`]%
 |rrrr|/<-`<-`<-`<-/[\alpha`\beta`\gamma`\delta]
 \efig$$
 This one is probably worth saving as a template.  Later I will explain
the meaning of the strings \verb.!{(300,1000);(500,1000)}\hole. and
 \verb.!{(1000,500);(1000,300)}\hole. along with a caveat on their use.
If the nodes are unusually large, the cube may be magnified using
\index{\backslash scalefactor}\verb.\scalefactor.  .

\subsection{Inline macros}
 Here we illustrate a few of the macros for inline---or
displayed---equations the package contains.  In each case, the macro may
have a superscript or subscript or both (in which case the superscript
must come first) and the arrow(s) grow long enough to hold the super- or
subscript.  If you type\par\noindent
\verb.$A\to B\to^f C\to_g D\to^h_{{\rm Hom}(X,Y)} E$., you get
 $A\to B\to^f C\to_g D\to^h_{{\rm Hom}(X,Y)} E$.  Similarly, the macro
\index{\backslash toleft}\verb.\toleft. reverses the arrows.  The remaining macros
of this sort are \index{\backslash mon}\verb.\mon. which gives a monic arrow,
\index{\backslash epi}\verb.\epi. which gives an epic arrow,
\index{\backslash two}\verb.\two. that gives a pair of arrows, as well as
leftwards pointing versions, \index{\backslash monleft}\verb.\monleft.,
\index{\backslash epileft}\verb.\epileft., and \index{\backslash twoleft}\verb.\twoleft. of
each of them.  Here is one more example:
\begin{verbatim}
 $A\twoleft B\twoleft^f C\twoleft_g D\twoleft^h_{{\rm Hom}(X,Y)} E$
\end{verbatim}
 gives  $A\twoleft B\twoleft^f C\twoleft_g D\twoleft^h_{{\rm Hom}(X,Y)} E$.
There is an almost unlimited variety of such procedures possible.  The
ones that are provided can be used as templates to define new ones with,
say, curved arrows or three arrows or whatever a user might have need
of.

\subsubsection{Added:}\label{added} The macros \index{\backslash to}\verb.\to. and
\index{\backslash two}\verb.\two. can each have optional parameters of the form
\index{/{sh}/<dx>}\verb./{sh}/<dx>. and
\index{/{sh}`{sh}/<dx>}\verb./{sh}`{sh}/<dx>., resp. that allow you to
specify the shapes of the arrows and to override the automatic
computation of the lengths of the arrows.  For example,
 \begin{verbatim}
$$A\to/<-/ B\to^f C \to/ >->/<500>_g D\to/<-< /^f_g E$$
$$A\two/<-`->/<100> B\two^f C \two/ >->` >->/_g D\two/<-< `<-< /^f_g E$$
\end{verbatim}
 gives
$$A\to/<-/ B\to^f C \to/ >->/<500>_g D\to/<-< /^f_g E$$
$$A\two/<-`->/<100> B\two^f C \two/ >->` >->/_g D\two/<-< `<-< /^f_g E$$
 This renders \index{\backslash mon}\verb.\mon., \index{\backslash epi}\verb.\epi.,
\index{\backslash toleft}\verb.\toleft., \index{\backslash monleft}\verb.\monleft.,
\index{\backslash epileft}\verb.\epileft., and \index{\backslash twoleft}\verb.\twoleft.
obsolete, but they have been retained for back compatibility and
convenience.  A three arrow macro that works similarly has been added.
For example
 \begin{verbatim}
 $$A\threepppp/>`<-`>/<400>^{d^0}|{s^0}_{d^1}B\three<100>
C\three/->>`<-< `->>/ D$$
\end{verbatim}
 gives
 $$A\threepppp/>`<-`>/<400>^{d^0}|{s^0}_{d^1}B\three<100>
C\three/->>`<-< `->>/ D$$

\subsection{2-arrows}
 There is a macro for making 2-arrows of a fixed size, but varying
orientation.  They should be put at the appropriate position in a
diagram.  The two parameters are two integers \index{dx}\verb.dx. and
\index{dy}\verb.dy. whose ratio is the slope of the arrow.  They need
not be relatively prime, but arithmetic overflow could occur if they are
too large.  Note that although \index{(dx,dy)}\verb.(dx,dy). and
\index{(-dx,-dy)}\verb.(-dx,-dy). describe the same slope, the arrows
point in opposite directions.  Here is a sampler
 \begin{verbatim}
 $$\bfig
 \place(0,0)[\twoar(1,0)]
 \place(200,0)[\twoar(0,1)]
 \place(400,0)[\twoar(1,1)]
 \place(600,0)[\twoar(0,-1)]
 \place(800,0)[\twoar(1,2)]
 \place(1000,0)[\twoar(1,3)]
 \place(1200,0)[\twoar(1,-3)]
 \place(1400,0)[\twoar(-3,1)]
 \place(1600,0)[\twoar(-1,-3)]
 \place(1800,0)[\twoar(255,77)]
 \efig$$
\end{verbatim}
 $$\bfig
 \place(0,0)[\twoar(1,0)]
 \place(200,0)[\twoar(0,1)]
 \place(400,0)[\twoar(1,1)]
 \place(600,0)[\twoar(0,-1)]
 \place(800,0)[\twoar(1,2)]
 \place(1000,0)[\twoar(1,3)]
 \place(1200,0)[\twoar(1,-3)]
 \place(1400,0)[\twoar(-3,1)]
 \place(1600,0)[\twoar(-1,-3)]
 \place(1800,0)[\twoar(255,77)]
 \efig$$

Here is little amusement.
\begin{verbatim}
 $$\bfig
 \square/@3{->}`~)`=o`--x/[A`B`C`D;```]
 \place(400,100)[\twoar(-1,-1)]
 \place(100,400)[\twoar(1,1)]
 \morphism(500,500)||/{*}.{*}/<-500,-500>[B`C;]
 \efig$$
\end{verbatim}
 $$\bfig
 \square/@3{->}`~)`=o`--x/[A`B`C`D;```]
 \place(400,100)[\twoar(-1,-1)]
 \place(100,400)[\twoar(1,1)]
 \morphism(500,500)||/{*}.{*}/<-500,-500>[B`C;]
 \efig$$

\subsection{Mixing \xypic\ code}
 Here is a sample in which I have mixed code from \xypic\ with my own.
\let\tilde\widetilde
\let\hat\widehat
\begin{verbatim}
 $$\bfig
 \square(1500,500)/>`>`>`@{>}^<>(.2){r_{n-1}}/[T_{n-1}`T_{n-2}`R_{n-1}
`R_{n-2}; t_{n-1}``\sigma_{n-2}`]
 \square(1500,0)/`>`>`>/[R_{n-1}`R_{n-2}`S_{n-1}`S_{n-2};
`f_{n-1}`f_{n-2}`s_{n-1}]
 \morphism|b|[\tilde S_{n+1}`S_n;\tilde s_{n+1}]
 \square(1000,500)/>`>`>`>/[\tilde T_n`T_{n-1}`\tilde
R_n`{R_{n-1}};\tilde t_n`\tilde \sigma_n`\sigma_{n-1}`]
 \square(1000,0)/>`>``>/[\tilde R_n`R_{n-1}`\tilde S_n`{S_{n-1}};\tilde
r_n\quad ```\tilde s_n]
 \square(500,0)/>`>``>/[R_n`{R_n}`{S_n}`{S_{n}};
\hat r_n`f_n`\tilde f_n`\hat s_n]
 \POS(1500,1000)*+!!<0ex,.75ex>{T_{n-1}}
 \ar@{-}|!{(1000,500);(1500,500)}\hole(1167,334)%
 \POS(1167,334)\ar|!{(1000,500);(1000,0)}\hole_<>(.6){h_{n-1}}
  (500,0)*+!!<0ex,.75ex>{S_n}
 \morphism(2000,1000)/@{>}|\hole^<>(.8){h_{n-2}}/%
 <-500,-1000>[T_{n-2}`S_{n-1};]
 \efig$$
\end{verbatim}
 $$\bfig
 \square(1500,500)/>`>`>`@{>}^<>(.2){r_{n-1}}/[T_{n-1}`T_{n-2}`R_{n-1}
`R_{n-2}; t_{n-1}``\sigma_{n-2}`]
 \square(1500,0)/`>`>`>/[R_{n-1}`R_{n-2}`S_{n-1}`S_{n-2};
`f_{n-1}`f_{n-2}`s_{n-1}]
 \morphism|b|[\tilde S_{n+1}`S_n;\tilde s_{n+1}]
 \square(1000,500)/>`>`>`>/[\tilde T_n`T_{n-1}`\tilde
R_n`{R_{n-1}};\tilde t_n`\tilde \sigma_n`\sigma_{n-1}`]
 \square(1000,0)/>`>``>/[\tilde R_n`R_{n-1}`\tilde S_n`{S_{n-1}};\tilde
r_n\quad ```\tilde s_n]
 \square(500,0)/>`>``>/[R_n`{R_n}`{S_n}`{S_{n}};
\hat r_n`f_n`\tilde f_n`\hat s_n]
 \POS(1500,1000)*+!!<0ex,.75ex>{T_{n-1}}
 \ar@{-}|!{(1000,500);(1500,500)}\hole(1167,334)%
 \POS(1167,334)\ar|!{(1000,500);(1000,0)}\hole_<>(.6){h_{n-1}}
  (500,0)*+!!<0ex,.75ex>{S_n}
 \morphism(2000,1000)/@{>}|\hole^<>(.8){h_{n-2}}/%
 <-500,-1000>[T_{n-2}`S_{n-1};]
 \efig$$
 There are three points to note here in connection with the two lines
that begin with \index{\backslash POS}\verb.\POS.  First the objects that are the
source of the first and the target of the second are preceded by
\verb;!!<0ex,.75ex>;\verb;!!<0ex,.75ex>;.  The effect is to reset the
baseline to the baseline of the object (rather than the vertical center)
and then to lower that by 3/4 of xheight so that the arrow goes in the
right place.  This string precedes all objects.  Without that, an object
like $\tilde R $ would be set lower that $R$.  Second, the first arrow
has no target and the second no source.  This does not give the same
result as empty source and target since in the latter cases, there would
be spaces allowed around them and then the two lines would not meet.  It
would be possible to add code that tests for empty nodes, but it comes
up so seldom that I have refrained.  In the meantime, the only recourse
is to revert to the underlying \xypic\ code.  Thirdly the string
\verb.|!{(1000,500);(1500,500)}\hole. specifies that the line should be
broken at the place where the current arrow intersects the line between
the nodes located at (1000,500) and (1500,500).  One must be careful
using this construction, however, as it does not seem to work correctly
if the line segment fails to intersect the current line, or if it does
intersect, but happens to be too long.  I have not worked out how long
is too long, but you can get odd results.  I assume that this bug will
be fixed eventually.  (Ross Moore says that it works correctly in the
version he has, which, however, has not been released.)  There is a
similar string, with similar effect, in the following line.  The last
line uses simply \index{|\hole}\verb.|\hole. which positions the gap in
the middle of the arrow.


\subsection{loops}
 Two new procedures \verb.\Loop. and \verb.\iloop. have been added, the
latter for inline loops.  (Note: \verb.\loop. was changed to
\verb.\Loop. as the former conflicted with amstex.) Here are
examples:
\begin{verbatim}
 $$\bfig
 \morphism[A`B;f]
 \Loop(0,0)A(ur,ul)_g
 \Loop(500,0)B(dl,dr)_h
 \efig$$
\end{verbatim}
 $$\bfig
 \morphism[A`B;f]
 \Loop(0,0)A(ur,ul)_g
 \Loop(500,0)B(dl,dr)_h
 \efig$$

Inline: Either \verb.$A\iloop B(ur,ul)C$.
or \verb.$\xy\Loop(0,0)A(ur,ul)\endxy$. gives the output $\xy
 \Loop(0,0)A(ur,ul)\endxy$.  The direction indicators show what
direction the loops start and end in.

\subsection{Diagram from TTT}\label{tttdiag}
 The last example is a complicated diagram from TTT.  If you have the
documentation from the old diagram macros (or the errata from TTT), you
can see how much easier it is to describe this diagram with these
macros.  Note the use of \index{\backslash scalefactor}\verb.\scalefactor. to
change the default length from 500 to 700 that made it unnecessary to
specify the scales on the squares and triangles.
 \begin{verbatim}
 $$\bfig
 \scalefactor{1.4}%
 \qtriangle(0,1000)/>`>`/[TT`T`TTT';\mu`TT\eta'`]%
 \btriangle(500,1000)/`>`@<-14\ul>/[T`TTT'`TT';`T\eta`T\sigma]%
 \morphism(0,1500)|l|/>/<0,-1000>[TT`TT'T;T\eta'T]%
 \square(500,500)|ammx|/@<14\ul>`>`>`/[TTT'`TT'`TT'TT'`TT'T';%
    \mu T'`T\eta'TT'`T\eta'T'`]%
 \morphism(1000,1000)|r|/>/<500,-500>[TT'`TT';\hbox{\rm id}]%
 \square/>`>``>/[TT'T`TT'TT'`T'T`T'TT';TT'T\eta'`\sigma T``T'T\eta']%
 \square(500,0)|ammb|[TT'TT'`TT'T'`T'TT'`T'T';%
    TT'\sigma`\sigma TT'`\sigma T'`T'\sigma T']%
 \square(1000,0)/>``>`>/[TT'T'`TT'`T'T'`T';T\mu'``\sigma`\mu']%
\place(500,1250)[1]\place(215,1000)[2]\place(750,750)[3]%
\place(215,250)[4]\place(750,250)[5]\place(1140,750)[6]%
\place(1250,250)[7]%
 \efig$$
\end{verbatim}
 $$\bfig\label{TTTdiag}
 \scalefactor{1.4}%
 \qtriangle(0,1000)/>`>`/[TT`T`TTT';\mu`TT\eta'`]%
 \btriangle(500,1000)/`>`@<-14\ul>/[T`TTT'`TT';`T\eta`T\sigma]%
 \morphism(0,1500)|l|/>/<0,-1000>[TT`TT'T;T\eta'T]%
 \square(500,500)|ammx|/@<14\ul>`>`>`/[TTT'`TT'`TT'TT'`TT'T';\mu T'`%
    T\eta'TT'`T\eta'T'`]%
 \morphism(1000,1000)|r|/>/<500,-500>[TT'`TT';\hbox{\rm id}]%
 \square/>`>``>/[TT'T`TT'TT'`T'T`T'TT';TT'T\eta'`\sigma T``T'T\eta']%
 \square(500,0)|ammb|[TT'TT'`TT'T'`T'TT'`T'T';TT'\sigma`\sigma TT'%
    `\sigma T'`T'\sigma T']%
 \square(1000,0)/>``>`>/[TT'T'`TT'`T'T'`T';T\mu'``\sigma`\mu']%
\place(500,1250)[1]\place(215,1000)[2]\place(750,750)[3]%
\place(215,250)[4]\place(750,250)[5]\place(1140,750)[6]%
\place(1250,250)[7]%
 \efig$$

Here is code that produces the same diagram using the new \verb.\arrow.
feature:
\begin{verbatim}
\node a(0,1500)[TT]%
\node b(500,1500)[T]%
\node c(500,1000)[TTT']%
\node d(1000,1000)[TT']%
\node e(0,500)[TT'T]%
\node f(500,500)[TT'TT']%
\node g(1000,500)[TT'T']%
\node h(1500,500)[TT']%
\node i(0,0)[T'T]%
\node j(500,0)[T'TT']%
\node k(1000,0)[T'T']%
\node l(1500,0)[T']%
 $$\bfig
\scalefactor{1.4}%
\arrow[a`b;\mu]%
\arrow|l|[a`e;T\eta'T]%
\arrow|l|[a`c;TT\eta]%
\arrow[b`d;T\eta]%
\arrow/@<14\ul>/[c`d;\mu T']%
\arrow|b|/@<-14\ul>/[c`d;T\sigma]%
\arrow[d`h;\mbox{id}]%
\arrow|m|[c`f;T\eta'TT']%
\arrow|m|[d`g;T\eta'T']%
\arrow[e`f;TT'T\eta']%
\arrow[f`g;TT'\sigma]%
\arrow[g`h;T\mu']%
\arrow|l|[e`i;\sigma T]%
\arrow|m|[f`j;\sigma TT']%
\arrow|m|[g`k;\sigma T']%
\arrow[h`l;\sigma]%
\arrow|b|[i`j;T'T\eta']%
\arrow|b|[j`k;T'\sigma T']%
\arrow[k`l;\mu']%
\place(500,1250)[1]\place(215,1000)[2]\place(750,750)[3]%%
\place(215,250)[4]\place(750,250)[5]\place(1140,750)[6]%%
\place(1250,250)[7]%
 \efig$$
\end{verbatim}
 It is in some ways easier than the other, but more verbose.  In the end
it comes down to a matter of preference.



\clearpage
\def\lab(#1,#2)[#3]{\place(#1,#2)[\backslash\hbox{\texttt#3}]}
\def\Lab[#1]{{\backslash\hbox{\texttt#1}}}


\section{A few comparisons with {\tt xymatrix}}

We give here a few diagrams to contrast the predefined shapes of
\verb.diagxy. with those produced by \verb.xymatrix..  These are not
intended to be invidious, but they are chosen to show \verb.xymatrix. in
the worst light.  The diagrams can be improved by using special options
of \verb.xymatrix. but the second diagrams are the default in
\verb.diagxy..  Of course, \verb.diagxy. uses \verb.xypic. but not the
\verb.xymatrix. option., so this is not meant as a putdown of
\verb.xypic., only as a comparison if you are trying to decide which to
use.  In the end, though you will probably decide on the basis of which
you feel most comfortable with.  Users of \verb.diagxy. like the
predefined shapes and others find the native syntax of \verb.xypic. more
comfortable.

\xyoption{matrix}
The first one illustrates what happens when the nodes are vertically
unbalanced.  Changing \verb.\xymatrix. to \verb.\xymatrix1@. improves
the appearance, but it is still not perfect.

\begin{verbatim}
$$\xymatrix {A^{X^Y}\ar[r]&B_{Z_W}\ar[r]&C}
\qquad A^{X^Y}\to B_{Z_W}\to C$$
\end{verbatim}
 produces
$$\xymatrix {A^{X^Y}\ar[r]&B_{Z_W}\ar[r]&C}
\qquad A^{X^Y}\to B_{Z_W}\to C$$

The next sample shows what happens to the label when the nodes are of
quite different length.  Putting a - after the \verb.^. fixes this.
\begin{verbatim}
$$\xymatrix{A\ar[r]^{(f,g,h)}&B\times C\times D}\qquad
A\to^{(f,g,h)}B\times C\times D$$
\end{verbatim}
 produces
$$\xymatrix{A\ar[r]^{(f,g,h)}&B\times C\times D}\qquad
A\to^{(f,g,h)}B\times C\times D$$


However, it doesn't fix the problem of too short an arrow.  Replacing
\verb.[r]. by \verb.[rr]. and the \verb.&. by \verb.&&. fixes this.
\begin{verbatim}
$$\xymatrix{A\ar[r]^-{(f_1,g_2,h_3)}&B\times C\times D}\qquad
A\to^{(f_1,g_2,h_3)}B\times C\times D$$
\end{verbatim}
 produces
$$\xymatrix{A\ar[r]^-{(f_1,g_2,h_3)}&B\times C\times D}\qquad
A\to^{(f_1,g_2,h_3)}B\times C\times D$$

Unbalanced nodes in a triangle result in an unbalanced triangle.  I do
not know how to fix this one up, although \verb.xypic. has so many
options that there is probably some way.
\begin{verbatim}
$$\xymatrix{A\ar[rr]\ar[dr]&&B\times C\times D\ar[dl]\\&E}$$
$$\xy\Vtriangle[A`B\times C\times D`E;``]\endxy$$
\end{verbatim}
 produces
$$\xymatrix{A\ar[rr]\ar[dr]&&B\times C\times D\ar[dl]\\&E}$$
$$\xy\Vtriangle[A`B\times C\times D`E;``]\endxy$$

\clearpage
\section{Thumbnails}

This page shows all the shapes that have been defined so far.  In all
cases, consult the documentation for the syntax and a discussion of the
optional parameters.  Note that \verb.\Square., along with
\verb.\hSquares. and \verb.\vSquares. grow in width to accomodate the
nodes and labels.

\scalefactor{.4}
 % \fontscale{}
\let\.\cdot
$\.\to_{\Lab[to]}\.\toleft_{\Lab[toleft]}\.
\mon_{\Lab[mon]}\.\monleft_{\Lab[monleft]}\.\epi_{\Lab[epi]}\.\epileft_{\Lab[epileft]}\.
\two_{\Lab[two]}\.\three_{\Lab[three]}\.$

 $$\bfig
 \square[\.`\.`\.`\.;```]
 \lab(200,-250)[square]
 \Atriangle(1000,0)[\.`\.`\.;``]
 \lab(1400,-250)[Atriangle]
 \Vtriangle(2500,0)[\.`\.`\.;``]
 \lab(2900,-250)[Vtriangle]
 \Ctriangle(4000,0)[\.`\.`\.;``]
 \lab(4400,-250)[Ctriangle]
 \Dtriangle(5000,0)[\.`\.`\.;``]
 \lab(5400,-250)[Dtriangle]
\def\ru{\.\.\.\.\.}
 \square(0,-1500)<1000,500>[\ru`\ru`\ru`\ru;```]
 \lab(400,-1750)[Square]
 \ptriangle(1800,-1500)[\.`\.`\.;``]
 \lab(2000,-1750)[ptriangle]
 \qtriangle(2900,-1500)[\.`\.`\.;``]
 \lab(3100,-1750)[qtriangle]
 \dtriangle(4000,-1500)[\.`\.`\.;``]
 \lab(4200,-1750)[dtriangle]
 \btriangle(5100,-1500)[\.`\.`\.;``]
 \lab(5400,-1750)[btriangle]
 \Atrianglepair(0,-3000)[\.`\.`\.`\.;````]
 \lab(400,-3250)[Atrianglepair]
 \Vtrianglepair(1500,-3000)[\.`\.`\.`\.;````]
 \lab(1900,-3250)[Vtrianglepair]
 \Ctrianglepair(3500,-3000)[\.`\.`\.`\.;````]
 \lab(3400,-3250)[Ctrianglepair]
 \Dtrianglepair(4500,-3000)[\.`\.`\.`\.;````]
 \lab(4900,-3250)[Dtrianglepair]
 \hSquares(0,-4500)[\ru`\ru`\ru`\ru`\ru`\ru;``````]
 \lab(600,-4750)[hSquares]
 \pullback(2700,-4500)[\.`\.`\.`\.;```][\.;``]
 \lab(3000,-4750)[pullback]
 \iiixii(4000,-4500){15}<400>[\.`\.`\.`\.`\.`\.;``````]
 \lab(4800,-4750)[iiixii]
 \cube(0,-7000)[\.`\.`\.`\.;```](500,-6500)[\.`\.`\.`\.;```][```]
 \lab(700,-7250)[cube]
 \iiixiii(2500,-7000)[\.`\.`\.`\.`\.`\.`\.`\.`\.;```````````]
 \lab(3000,-7250)[iiixiii]
 \vSquares(4500,-7000)[\ru`\ru`\ru`\ru`\ru`\ru;``````]
 \lab(4800,-7250)[vSquares]
 \efig$$

 \clearpage
\section{Command summary}

\def\v#1.{{\texttt{#1}}}
 Below is a summary of the syntax of the supplied shapes.  In this
summary, optional parameters are enclosed in braces (\verb/{}/) because
the more usual brackets are too much used.  In only two cases below are
braces to be used and they will be made clear.  In all cases it is the
set of parameters that is optional; you must accept the default for all,
or set them all.  But the different sets of parameters are independent.
Note that continuation lines are marked with a \verb.%. sign.  If you
break one of these macros be sure to end the line with \verb.%., unless
you are inside the \verb/[...]/, where everything is done in math mode
and space characters are ignored.
\begin{trivlist}
 \item[\v(x,y).:] The coordinates of the lower left corner of the
smallest rectangle that encloses the figure, whether or not that corner
is actually in the shape.

\item[\v p.:]
One of the letters \v a., \v b., \v l.,
\v m., or \v x. and describe the placement of an arrow label as above,
below, right, left,in the middle of an arrow, or no label, resp.

\item[\v a.:] The shape of the arrow.

\item[\v <dx,dy>.:]  The horizontal and vertical extent of the diagram.
In a couple cases only one is specified.

\item[\v O.:] An object or node.

\item[\v L.:] An arrow label.

\item[\v N.:] A number in the range 0..15.  If it has more than one
digit, must be placed inbraces.

\item[\v M.:] A number in the range 0.."7777.  Also in braces.

\end{trivlist}


\begin{verbatim}
\to{/a/}{^A}{|A}{_A}
\xar{^A}{|A}{_A}(xar = mon, epi, toleft, monleft, epileft)
\square{(x,y)}{|pppp|}{/a`a`a`a/}{<dx,dy>}[O`O`O`O;L`L`L`L]
\Ltriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\Vtriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\Ctriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\Dtriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\Square{(x,y)}{|pppp|}{/a`a`a`a/}{<dy>}[O`O`O`O;L`L`L`L]
\ptriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\qtriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\dtriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\btriangle{(x,y)}{|ppp|}{/a`a`a/}{<dx,dy>}[O`O`O;L`L`L]
\Ltrianglepair{(x,y)}{|ppppp|}{/a`a`a`a`a/}{<dx,dy>}%
     [O`O`O`O;L`L`L`L`L]
\Vtrianglepair{(x,y)}{|ppppp|}{/a`a`a`a`a/}{<dx,dy>}%
     [O`O`O`O;L`L`L`L`L]
\Ctrianglepair{(x,y)}{|ppppp|}{/a`a`a`a`a/}{<dx,dy>}%
     [O`O`O`O;L`L`L`L`L]
\Dtrianglepair{(x,y)}{|ppppp|}{/a`a`a`a`a/}{<dx,dy>}%
     [O`O`O`O;L`L`L`L`L]
\hSquares{(x,y)}{|ppppppp|}{/a`a`a`a`a`a`a/}{<dx,dy>}%
     [O`O`O`O`O`O;L`L`L`L`L`L`L]
\pullback{(x,y)}{|pppp|}{/a`a`a`a/}{<dx,dy>}[O`O`O`O;L`L`L`L]
     {|ppp|}{/a`a`a/}{<#7,#8>}[O;L`L`L]
\iiixii{(x,y)}{|ppppppp|}{/a`a`a`a`a`a`a/}{<dx,dy>}%
     {N{<dx,dy>}}[O`O`O`O`O`O;L`L`L`L`L`L`L]
\cube{(x,y)}{|pppp|}{/a`a`a`a/}{<dx,dy>}[O`O`O`O;L`L`L`L]%
     {(x,y)}{|pppp|}{/a`a`a`a/}{<dx,dy>}[O`O`O`O;L`L`L`L]%
     {|pppp|}{/a`a`a`a/}[L`L`L`L]
\iiixiii{(x,y)}{|pppppppppppp|}{/a`a`a`a`a`a`a`a`a`a`a`a/}%
     {<dx,dy>}{M{<dx>}}%
     [O`O`O`O`O`O`O`O`O;L`L`L`L`L`L`L`L`L`L`L`L`L`L`L]
\vSquares{(x,y)}{|ppppppp|}{/a`a`a`a`a`a`a/}{<dx,dy>}%
           [O`O`O`O`O`O;L`L`L`L`L`L`L]
\end{verbatim}


\edef\backslash{\ensuremath{\backslash}}
\catcode`\<=\active
\catcode`\>=\active
\catcode`\^=\active
\catcode`\_=\active
\def<{\mathhexbox13C}
\def>{\mathhexbox13E}
\def^{\mathhexbox362}
\def_{\vrule width 10pt height .4pt depth 0pt}
\addcontentsline{toc}{section}{Index}
\newpage
\input diaxydoc.ind


\end{document}




If the shape parameter begins with an \index{@}\verb.@., it is
interpreted differently.  In that case, it has the form
\index{@{shape}@}\verb.@{shape}@. modifier, where the modifier is as
described in the \xypic\ reference guide.  I just mention a couple of
them.  The parameter \index{@{->}@<3pt>}\verb.@{->}@<3pt>., for example,
would give an ordinary arrow moved three points in the direction
perpendicular to that of the arrow.  If you give
\index{{@{->>}@/^5pt/}}\verb.{@{->>}@/^5pt/}., you will get an epic
arrow that is curved in the direction perpendicular to the direction of
the arrow by five points.  It is imperative that a specification such as
\index{@{>}@/5pt/}\verb.@{>}@/5pt/. be enclosed in braces because of the
\index{/}\verb./.s.
