Predefined Syntaxes
===================

  If you're programming with Regex, you can set a pattern buffer's
(see GNU Pattern Buffers., and See POSIX Pattern Buffers)
`syntax' field either to an arbitrary combination of syntax bits (
see Syntax Bits.) or else to the configurations defined by Regex.  These
configurations define the syntaxes used by certain programs--GNU Emacs,
POSIX Awk, traditional Awk, Grep, Egrep--in addition to syntaxes for
POSIX basic and extended regular expressions.

  The predefined syntaxes-taken directly from `regex.h'--are:

     #define RE_SYNTAX_EMACS 0
     
     #define RE_SYNTAX_AWK                                                   \
       (RE_BACKSLASH_ESCAPE_IN_LISTS | RE_DOT_NOT_NULL                       \
        | RE_NO_BK_PARENS            | RE_NO_BK_REFS                         \
        | RE_NO_BK_VBAR               | RE_NO_EMPTY_RANGES                   \
        | RE_UNMATCHED_RIGHT_PAREN_ORD | RE_NO_GNU_OPS)
     
     #define RE_SYNTAX_GNU_AWK                                               \
       (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS)
     
     #define RE_SYNTAX_POSIX_AWK                                             \
       (RE_SYNTAX_GNU_AWK | RE_NO_GNU_OPS)
     
     #define RE_SYNTAX_GREP                                                  \
       (RE_BK_PLUS_QM              | RE_CHAR_CLASSES                         \
        | RE_HAT_LISTS_NOT_NEWLINE | RE_INTERVALS                            \
        | RE_NEWLINE_ALT)
     
     #define RE_SYNTAX_EGREP                                                 \
       (RE_CHAR_CLASSES        | RE_CONTEXT_INDEP_ANCHORS                    \
        | RE_CONTEXT_INDEP_OPS | RE_HAT_LISTS_NOT_NEWLINE                    \
        | RE_NEWLINE_ALT       | RE_NO_BK_PARENS                             \
        | RE_NO_BK_VBAR)
     
     #define RE_SYNTAX_POSIX_EGREP                                           \
       (RE_SYNTAX_EGREP | RE_INTERVALS | RE_NO_BK_BRACES)
     
     /* P1003.2/D11.2, section 4.20.7.1, lines 5078ff.  */
     #define RE_SYNTAX_ED RE_SYNTAX_POSIX_BASIC
     
     #define RE_SYNTAX_SED RE_SYNTAX_POSIX_BASIC
     
     /* Syntax bits common to both basic and extended POSIX regex syntax.  */
     #define _RE_SYNTAX_POSIX_COMMON                                         \
       (RE_CHAR_CLASSES | RE_DOT_NEWLINE      | RE_DOT_NOT_NULL              \
        | RE_INTERVALS  | RE_NO_EMPTY_RANGES)
     
     #define RE_SYNTAX_POSIX_BASIC                                           \
       (_RE_SYNTAX_POSIX_COMMON | RE_BK_PLUS_QM)
     
     /* Differs from ..._POSIX_BASIC only in that RE_BK_PLUS_QM becomes
        RE_LIMITED_OPS, i.e., \? \+ \| are not recognized.  Actually, this
        isn't minimal, since other operators, such as \`, aren't disabled.  */
     #define RE_SYNTAX_POSIX_MINIMAL_BASIC                                   \
       (_RE_SYNTAX_POSIX_COMMON | RE_LIMITED_OPS)
     
     #define RE_SYNTAX_POSIX_EXTENDED                                        \
       (_RE_SYNTAX_POSIX_COMMON | RE_CONTEXT_INDEP_ANCHORS                   \
        | RE_CONTEXT_INDEP_OPS  | RE_NO_BK_BRACES                            \
        | RE_NO_BK_PARENS       | RE_NO_BK_VBAR                              \
        | RE_UNMATCHED_RIGHT_PAREN_ORD)
     
     /* Differs from ..._POSIX_EXTENDED in that RE_CONTEXT_INVALID_OPS
        replaces RE_CONTEXT_INDEP_OPS and RE_NO_BK_REFS is added.  */
     #define RE_SYNTAX_POSIX_MINIMAL_EXTENDED                                \
       (_RE_SYNTAX_POSIX_COMMON  | RE_CONTEXT_INDEP_ANCHORS                  \
        | RE_CONTEXT_INVALID_OPS | RE_NO_BK_BRACES                           \
        | RE_NO_BK_PARENS        | RE_NO_BK_REFS                             \
        | RE_NO_BK_VBAR          | RE_UNMATCHED_RIGHT_PAREN_ORD)