(a2ps.info)Implementation

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7.7.2 Implementation
--------------------

Quite naturally the style will be called 'ChangeLog', hence:
     style ChangeLog is
     written by "Akim Demaille <demaille@inf.enst.fr>"
     version is 1.0
     requires a2ps 4.9.5

     documentation is
        "This is a tutorial style sheet.\n"
     end documentation
       ...
     end style

   A first interesting and easy entry is that of function names, between
'(' and ')':
     sequences are
       "(" Plain Label ")" Plain
     end sequences

   A small problem that may occur is that there can be several functions
mentioned separated by commas, that we don't want to highlight this way.
Commas, here, are exceptions.  Since regular expressions are not yet
implemented in a2ps, there is a simple but stupid way to avoid that
white spaces are all considered as part of a function name, namely
defining two exceptions: one which captures a single comma, and a
second, capturing a comma and its trailing space.

   For the file names, the problem is a bit more delicate, since they
may end with ':', or when starts the list of functions.  Then, we define
two sequences, each one with one of the possible closers, the exceptions
being attached to the first one:

     sequences are
       "* " Plain Label_strong ":" Plain
          exceptions are
             ", " Plain, "," Plain
          end exceptions,
       "* " Plain Label_strong " " Plain
     end sequences

   Finally, let us say that some words have a higher importance in the
core of text: those about removing or adding something.
     keywords in Keyword_strong are
       add, added, remove, removed
     end keywords

   Since they may appear in lower or upper, of mixed case, the style
will be defined as case insensitive.

   Finally, we end up with this style sheet file, in which an optional
highlighting of the mail address of the author is done.  Saving the file
is last step.  But do not forget that a style sheet has both a name as
nice as you may want (such as 'Common Lisp'), and a key on which there
are strict rules: the prefix must be alpha-numerical, lower case, with
no more than 8 characters.  Let's chose 'chlog.ssh'.

     # This is a tutorial on a2ps' style sheets
     style ChangeLog is
     written by "Akim Demaille <demaille@inf.enst.fr>"
     version is 1.0
     requires a2ps 4.9.5

     documentation is
        "Second level of high lighting covers emails."
     end documentation

     sequences are
       "(" Plain Label ")" Plain
          exceptions are
             ", " Plain, "," Plain
          end exceptions,
       "* " Plain Label_strong ":" Plain
          exceptions are
             ", " Plain, "," Plain
          end exceptions,
       "* " Plain Label_strong " " Plain
     end sequences

     keywords in Keyword_strong are
       add, added, remove, removed
     end keywords

     optional sequences are
        < Plain Keyword > Plain
     end sequences
     end style

   As a last step, you may which to let a2ps check your style sheet,
both its syntax, and common errors:
     ubu $ a2ps -vsheet -E/tmp/chlog.ssh ChangeLog -P void
     Long output deleted
     Checking coherence of "ChangeLog" (/tmp/chlog.ssh)
     "ChangeLog" (/tmp/chlog.ssh) is sane.
     ---------- End of Finalization of /tmp/chlog.ssh

   It's all set, your style sheet is ready!