shy groups.
@item \(?: @dots{} \)
+@cindex shy groups
+@cindex non-capturing group
+@cindex unnumbered group
is the @dfn{shy group} construct. A shy group serves the first two
purposes of an ordinary group (controlling the nesting of other
operators), but it does not get a number, so you cannot refer back to
-its value with @samp{\@var{digit}}.
+its value with @samp{\@var{digit}}. Shy groups are particularly
+useful for mechanically-constructed regular expressions, because they
+can be added automatically without altering the numbering of ordinary,
+non-shy groups.
-Shy groups are particularly useful for mechanically-constructed regular
-expressions because they can be added automatically without altering the
-numbering of any ordinary, non-shy groups.
+Shy groups are also called @dfn{non-capturing} or @dfn{unnumbered
+groups}.
@item \(?@var{num}: @dots{} \)
is the @dfn{explicitly numbered group} construct. Normal groups get
@defun regexp-opt-depth regexp
This function returns the total number of grouping constructs
-(parenthesized expressions) in @var{regexp}. (This does not include
-shy groups.)
+(parenthesized expressions) in @var{regexp}. This does not include
+shy groups (@pxref{Regexp Backslash}).
@end defun
@node Regexp Search