7.6.5 Syntax for the P-Rules

See 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 ‘(’. See Regular Expression Syntax in Regex manual, 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.