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       prerex_format -- a format for prerequisite-chart descriptions


       This  manual describes the format of prerequisite-chart descriptions that can be processed
       by [pdf]latex (normally using a suitable prerex.sty(7) style file) and  edited  using  the
       prerex(1) interactive editor (or by any conventional text editor).


       A  prerequisite chart consists of a number of course boxes, linked by arrows.  Courses are
       either half or full, and may be required or optional (or neither).  Each  course  box  can
       contain  a  course  code  (upper  left corner), a course title (lower half), and timetable
       information (upper right corner).  An arrow  can  be  either  a  prerequisite  (solid),  a
       corequisite  (dotted),  or  recommended  (dashed).   When  a  conventional  arrow would be
       inappropriate, a mini course just above a target box can be used.


       The file should contain exactly one instance of a LaTeX environment

       \begin{chart} instruction ... \end{chart}

       with at most one instruction per line.  Note that a program  such  as  prerex(1)  analyzes
       prerex-format  files without using TeX; for example, macro definitions will be ignored and
       macro calls will not be expanded.

       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 precede  the  instruction  for
       the arrow.  The instruction formats are described in the following sections.


       The instructions producing course boxes have the following forms:

       \halfcourse x,y:{code}{title}{timetable}

       \fullcourse x,y:{code}{title}{timetable}

       \reqhalfcourse x,y:{code}{title}{timetable}

       \reqfullcourse x,y:{code}{title}{timetable}

       \opthalfcourse x,y:{code}{title}{timetable}

       \optfullcourse x,y:{code}{title}{timetable}

       where x,y are the coordinates of the centerpoint of the box, relative to the origin of the
       coordinate system at the lower-left corner of the diagram.  The code, title, and 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:

              \halfcoursec x,y:{code}{title}{timetable}{color}

              \fullcoursec x,y:{code}{title}{timetable}{color}

              \reqhalfcoursec x,y:{code}{title}{timetable}{color}

              \reqfullcoursec x,y:{code}{title}{timetable}{color}

              \opthalfcoursec x,y:{code}{title}{timetable}{color}

              \optfullcoursec x,y:{code}{title}{timetable}{color}


       A mini course is produced by an instruction of the form

       \mini x,y:{code}

       A text line is inserted into the chart by an instruction of the form

       \text x,y:{line-of-text}

       The maximum allowed length of a course-code may be smaller that the maximum allowed for  a
              line of text.


       Arrows  between course boxes (or from a mini to a course box) are produced by instructions
       of the form

       \prereq x0,y0,x1,y1:

       \coreq x0,y0,x1,y1:

       \recomm x0,y0,x1,y1:

       These produce, respectively, solid, dotted, and dashed arrows  from  the  course  box  (or
       mini) centered at coordinates x0,y0 to the course box centered at coordinates x1,y1.

       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

       \prereqc x0,y0,x1,y1;c:

       \coreqc x0,y0,x1,y1;c:

       \recommc x0,y0,x1,y1;c:

       where c is an integer in the range -100:100 specifying the desired curvature; for example,
       c=0 will produce a straight arrow. To change the default curvature, the user  program  may
       redefine the \DefaultCurvature command.


       The  following  instruction  produces  a  coordinate  grid,  which is useful for editing a


       This is normally placed before all the other instructions so that grid lines  are  in  the
       background, covered by course boxes, minis, and arrows.


       Course  boxes  may be linked to web addresses.  The URL for course boxes may be set by the
       user by redefining the \CourseURL command; when called for a course box,  it  is  supplied
       with  three arguments, the x and y coordinates of the box, mini, or textline, and the code
       argument of the course box. For example,


       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.


       R. D. Tennent (


       prerex(1), prerex.sty(7).