Hi, the documentation for regexp says:
| -- Builtin: regexp (STRING, REGEXP, [REPLACEMENT]) | Searches for REGEXP in STRING. The syntax for regular expressions | is the same as in GNU Emacs, which is similar to BRE, Basic | Regular Expressions in POSIX. *Note Syntax of Regular | Expressions: (emacs)Regexps. Support for ERE, Extended Regular | Expressions is not available, but will be added in GNU M4 2.0. | [...] However: | [tim@passepartout ~]$ m4 | regexp(`abc', `\(b\)') | 1 | regexp(`abc', `\(?:b\)') | -1 | [tim@passepartout ~]$ Emacs's documentation on "Backslash in Regular Expressions" that is linked from m4's info file doesn't seem to imply that shy groups were in fact ERE. So is this a bug? Tim
