-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to Mike Frysinger on 4/6/2009 3:43 PM: >>> m4_define([_AS_IF_ELSE], >>> [m4_ifvaln([$1], >>> -[else >>> +[else : >>> $1])]) >>> >>> m4_defun([AS_IF], >> I like this one, for simplicity and obvious correctness alone, but will >> defer to Eric for the final decision. > > personally, i prefer both :). dont emit extraneous brackets when they arent > needed, and be safe when we think we must.
I'm also leaning towards omitting the else if $1 is provably blank, otherwise providing the : in case non-blank $1 ultimately expands to a blank (unless someone finds a shell where 'if false ; then :; fi; echo $?' fails to output 0). AS_CASE and AS_FOR are also candidates for this. And it will be easier with m4_ifblank. Stay tuned; I'll have a patch by the end of the week. Now for a question - right now, m4_default([$1], [$2]) is a nice shorthand for m4_ifval([$1], [$1], [$2]); is there any reason to create a shorthand for m4_ifnblank([$1], [$1], [$2]) that likewise only needs two arguments? And if so, what to call it? >> BTW, m4_normalize would have been wrong as it can change expanded text >> that you wouldn't want changed, too. (I think.) > > but that wouldnt matter would it ? we're only expanding to check it > ifvaln(normalize($1)). if we like the result, then we emit $1 as part of the > else. but again, m4 subtleties are beyond me. Actually, you nailed the subtleties on that one: m4_ifval(m4_normalize([$1]), [else : $1 ]) uses two copies of $1; the first can undergo arbitrary change to check for blanks, while the second is used as-is. I'd use exactly that if it weren't for the fact that the future m4_ifblank is more efficient than m4_ifval/m4_normalize. - -- Don't work too hard, make some time for fun as well! Eric Blake e...@byu.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAknauYgACgkQ84KuGfSFAYAW0wCcCdQaXVK+3zkxA1fQ15DDca2E Q8YAn1NVAGo58KaUumgZgemx75Fjk3Ea =tBx2 -----END PGP SIGNATURE----- _______________________________________________ Autoconf mailing list Autoconf@gnu.org http://lists.gnu.org/mailman/listinfo/autoconf
