Hi Dan, nice piece of work, thank you. On Mon, Feb 07, 2005 at 03:55:49PM -0500, Dan Manthey wrote: > > 3) ad: the implementation of non-recursive substitution: > > > > All the hacks with |#@!@#| are too complicated and not general enough. > > There is a better solution. > > > I agree that your solution works and makes non-recursion invisible > to the user, but I think it's actually benefitial to have the wacky string > that gets deleted (for instance, to disabiguate `@foo@bar@' by > `@foo@|#_!!_#|bar@'), so I have not taken your suggestion here. You are right, this is a good solution. > I just surround all `@'s with the deleted string, and also put it at the > beginning of each output value. I think adding the string _after_ each `@' would be enough; IOW I propose to change s/@/|#_!!_#|@|#_!!_#|/g to s/@/@|#_!!_#|/g To prove formally that it is correct, we have to prove that each `@foo@' which appears in any stage, was already in the original input. Proof: Let's have an occurence of `@foo@'. If its left `@' wasn't in the original input, then it has to be followed by |#_!!_#|, so it's not `@foo', contradiction. So the left `@' had to be inthe original line. If some characters of this occurence `@foo@' were inserted by a previous substitution, then there would have to be the |#_!!_#| from the beginning of the substituted value. Thus the whole `@foo@' had to be in the original line, q.e.d. > Note that I changed the deleted string to > be a palendrome, since that allows it to be inserted at its own center. What? IIRC, the previous suggestion was |#_!_#|, which is also a palendrome. No big deal, of course. One more comment: I notice that your patch contains m4_define([_AC_SED_CMDS],m4_defn([_AC_SED_CMDS])[| sed 's/|#_!!_#|//g' ]) As I have admitted before, I don't (yet) fully understand your patch, but this seems a bit suspicious to me. Does this mean that you use one more `sed' call in the pipe to remove these tokens? It's clear that you cannot put s/|#_!!_#|//g at the end of each fragment, But I think you can put it as the very last command of the last fragment. Oh yes, you have to change the last fragment to: /@[a-zA-Z_][a-zA-Z_0-9]*@/!b end ... :end s/|#_!!_#|//g but I think it's worth it. (Perhaps it would help to put the label `:end' at the end of each fragment, so that the first command of each fragment will be the same. You can decrease the number of commands for each segment by 2 (the label plus possibly s/|#_!!_#|//g). All this is still better than having one more process in the pipe. Will you find time to implement these improvements? > My thanks go to Stepan for all the help he's given with this. I'm glad to generate hints. But I have stated several times that I cannot keep pace with you and I actually don't understand your code. ;-) Thank you for this, Dan. It's really inspiring work! Have a nice day, Stepan _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
