(a2ps.info)Syntax for the P-Rules

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7.6.5 Syntax for the P-Rules
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Note: P-Rules, for the definition of "P-rule".

   Because of various short cuts, there are many ways to declare a rule:
     RULES     ::= RULE_1 ',' RULE_2...
     RULE      ::= '(' LHS RHS ')'
                | LHS SRHS ;
     LHS       ::= STRING | REGEX ;
     RHS       ::= SRHS ',' ...
     SRHS      ::= LATEX-KEYWORD | EXPANSION FACE
     EXPANSION ::= STRING | '\'NUM | <nothing>;
     FACE      ::= FACE-KEYWORD | <nothing>;

   The rules are the following:
   - If the left-hand side (lhs) is a regular expression, then it is
     compiled with the following syntax bits:
          #define RE_SYNTAX_A2PS \
            (/* Allow char classes. */					\
              RE_CHAR_CLASSES						\
            /* Be picky. */						\
            | RE_CONTEXT_INVALID_OPS					\
            /* Allow intervals with `{' and `}', forbid invalid ranges. */\
            | RE_INTERVALS | RE_NO_BK_BRACES | RE_NO_EMPTY_RANGES		\
            /* `(' and `)' are the grouping operators. */			\
            | RE_NO_BK_PARENS						\
            /* `|' is the alternation. */					\
            | RE_NO_BK_VBAR)

     Basically it means that all of the possible operators are used, and
     that they are in non-backslashed form.  For instance '(' and ')'
     stand for the group operator, while '\\(' stands for the character
     '('.  Note: Regular Expression Syntax,
 for a detailed description of the regular expressions.

   - If no EXPANSION is specified, then the matched string is used.  For
     instance '(/fo*/, NULL, Keyword)' applied on the source 'fooooo'
     produces 'fooooo' in 'Keyword'.

   - If no FACE is given, then
        - if the context defines the default face, then this face is
          used;

        - if no default face is given, 'PLAIN' is used.