-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I have often found myself wanting a subset of the currently defined macros that matches a regular expression or glob. But there's no easy way to get at it, even with the new m4symbols macro on the head, because you have to know the names of the subset in advance (the manual documents a way to double-quote the output of m4symbols, then pass that through a foreach loop to filter it, but it is not very efficient; and while it can do regex, it can't do glob matching since m4 currently has no globbing builtins[1]). What do others think of the following proposal for redefining the semantics of m4symbols? Note that since there has been no release with this macro, we can still tweak the semantics before M4 2.0.
Note that other builtins which take a list of macros will not change semantics - they still take literal lists, for several reasons. One, some of them are specified by POSIX (think dumpdef, traceon, popdef) to take literal lists, with no room for extensions. Two, these macros have been in previous M4 releases, so unlike m4symbols, we can't gratuitously break backwards compatibility. And three - simply use m4symbols' proposed powers to generate a literal list to feed the other macros (similar to how eval can take arbitrary expressions and turn them into decimal numbers to feed to other macros like divert that only parse decimal). m4symbols m4symbols([`list'], name...) m4symbols(`glob', pattern...) m4symbols(`match', [resyntax], pattern...) With no arguments, list all symbols. If the first argument is `glob', all remaining arguments are treated as globs, and all symbols matching each glob are listed (hmm - should symbols matching multiple globs be listed multiple times? Should the list be fully sorted[2], or just sorted for each glob, or unsorted?) If the first argument is `match' (or maybe also `regexp', except that regexp is a builtin by default while match is not), the remaining patterns are regular expressions rather than globs (same questions as for glob). Additionally, if the second argument is not blank, and matches a resyntax flavor (such as basic or extended; as in changeresyntax), the patterns have that syntax (a blank is ignored, necessary if you want to use the name of a resyntax flavor as the pattern but without changing the resyntax flavor; otherwise, if the second argument is not a resyntax flavor, it is silently treated as the first regex pattern using the current default flavor). If the first argument is `list' (necessary if you want to list the macro `glob' rather than turning on glob matching), or if the first argument does not match any reserved key, then all arguments are taken as literal macro names to list. [1] (I guess it would be nice to add a globbing builtin as well. On the other hand, I seem to recall that globs are a subset of regex - ie. you can convert any valid glob into a valid regex, although the converse is not always possible. So maybe you could argue that we already have globbing if you can just translate the pattern correctly). [2] The current implementation of m4symbols fully sorts the output, matching the way that dumpdef operates. This can be exploited to perform sorting of arbitrary lists - for each element in the list, pushdef an empty macro with a common prefix and the element as a suffix, then pipe the list through m4symbols for sorting, and post-process the list to popdef the temporary symbol and remove the prefix. Not the fastest or best use of memory in doing the sorting, but since we don't have any other builtin that sorts or even does lexicographic comparisons, it is rather interesting to consider. - -- Don't work too hard, make some time for fun as well! Eric Blake [EMAIL PROTECTED] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHt0Ou84KuGfSFAYARAtT9AKCxOJmWIoS/DgK3bH9Om0osz1a7xgCgtPTO SbPn9Tz4IlQIuLoEUCvP45I= =ea1H -----END PGP SIGNATURE----- _______________________________________________ M4-discuss mailing list M4-discuss@gnu.org http://lists.gnu.org/mailman/listinfo/m4-discuss
