.TH PREREX 5 2019-11-15 "prerex_format" ""
.SH NAME
prerex_format -- a format for prerequisite-chart descriptions 
.SH DESCRIPTION
This manual describes the format of 
prerequisite-chart descriptions that can be processed by 
.B [pdf]latex
(normally using
a suitable 
.BR  prerex.sty  (7)
style file) and edited using the
.BR prerex (1)
interactive editor (or by any conventional text editor).
.SH TERMINOLOGY
A prerequisite chart consists of a number of 
.I course boxes,
linked by 
.I arrows.
Courses are either
.I half
or
.I full,
and may be
.I required
or
.I optional
(or neither).
Each course box can contain a course
.I code
(upper left corner),
a course 
.I title
(lower half),
and
.I timetable
information
(upper right corner).
An arrow can be either a
.I prerequisite 
(solid),
a
.I corequisite 
(dotted),
or 
.I recommended
(dashed).
When a conventional arrow would be inappropriate,
a
.I mini 
course just above a target box can be used.
.SH STRUCTURE
The file should contain exactly one instance of a LaTeX environment
.P
.BI \ebegin{chart} " instruction ... " \eend{chart}
.P
with at most one 
.I instruction
per line.
Note that a program such as 
.BR prerex (1)
analyzes prerex-format files 
.I without 
using TeX; for example, 
macro definitions will be ignored and
macro calls will 
not be
expanded.
.PP
Instructions may be preceded by white space.
Lines that start with % are treated as comments and ignored.
The order of instructions is not significant except
that the instruction for the source and target box o an arrow should 
.I precede
the instruction for the arrow. 
The instruction formats are described in the following
sections.
.SH COURSE BOXES
The instructions producing course boxes have the following forms:
.HP 
.BI \ehalfcourse " x,y" :{ code }{ title }{ timetable }
.HP
.BI \efullcourse " x,y" :{ code }{ title }{ timetable }
.HP
.BI \ereqhalfcourse " x,y" :{ code }{ title }{ timetable }
.HP
.BI \ereqfullcourse " x,y" :{ code }{ title }{ timetable }
.HP
.BI \eopthalfcourse " x,y" :{ code }{ title }{ timetable }
.HP
.BI \eoptfullcourse " x,y" :{ code }{ title }{ timetable }
.LP
where
.I x,y
are the coordinates of the 
.I centerpoint 
of the box, relative to the origin
of the coordinate system at the lower-left corner of the diagram.
The 
.I code,
.I title,
and
.I timetable
arguments are arbitrary (well-bracketed) text, possibly with LaTeX markup.

The following are similar but take an additional argument to specify the (non-default)
background color of the course box:
.IP 
.BI \ehalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.IP
.BI \efullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.IP
.BI \ereqhalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.IP
.BI \ereqfullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.IP
.BI \eopthalfcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.IP
.BI \eoptfullcoursec " x,y" :{ code }{ title }{ timetable }{ color }
.LP

.SH MINI COURSE BOXES AND TEXT
A mini course is produced by an instruction of the form
.HP 
.BI \emini " x,y" :{ code }
.HP
A text line is inserted into the chart by an instruction of the form
.HP
.BI \etext " x,y" :{ line-of-text }
.HP
The maximum allowed length of a course-code may be smaller that the
maximum allowed for a line of text.
.SH ARROWS
Arrows between course boxes (or from a mini to a course box) are produced
by instructions of the form
.HP
.BI \eprereq " x0,y0,x1,y1" :
.HP
.BI \ecoreq " x0,y0,x1,y1" :
.HP
.BI \erecomm " x0,y0,x1,y1" :
.LP
These produce, respectively, solid, dotted, and dashed arrows from
the course box (or mini) centered at coordinates
.I x0,y0
to the course box centered at coordinates
.I x1,y1.
.PP
In some implementations, 
certain arrows by default have a
non-zero curvature.  It is possible to override the default curvature 
for a particular arrow by using
the instructions
.HP
.BI \eprereqc " x0,y0,x1,y1;c" :
.HP
.BI \ecoreqc " x0,y0,x1,y1;c" :
.HP
.BI \erecommc " x0,y0,x1,y1;c" :
.LP
where
.I c
is an integer in the range -100:100 specifying the desired curvature; for example, 
.IR c= 0
will produce a 
.I straight 
arrow. To change the default curvature, the user program may redefine the
.B \eDefaultCurvature
command.
.SH COORDINATE GRID
The following instruction produces a coordinate grid, which is
useful for editing a diagram: 
.HP
.B \egrid 
.LP
This is normally placed before all the other instructions so that
grid lines are in the background, covered by course boxes, minis, and arrows.
.SH WEB LINKS
Course boxes may be linked to web addresses.  
The URL for course boxes may be set by the user by redefining the
.B \eCourseURL 
command; when called for a course box, it is supplied with three arguments, the
.I x
and
.I y
coordinates of the box, mini, or textline, and
the
.I code
argument
of the course box. For example,
.HP
.B \erenewcommand{\eCourseURL}[3]{http://www.cs.queensu.ca/undergraduate/courses/#3.html}
.LP
is appropriate for courses at the School of Computing, Queen's University.
The first two arguments can be used to display the coordinates of a box, mini, or
textline in some PDF viewers while the mouse hovers over it when the source
file is being edited.
.SH AUTHOR
R. D. Tennent (rdt@cs.queensu.ca)
.SH SEE ALSO
.BR prerex (1),
.BR prerex.sty (7).