On Sat, Feb 22, 2025 at 1:54 AM Robert Elz <k...@munnari.oz.au> wrote:
> > > That is, in the example > > printf '%s %3$s %s\n' A B C D > > The updated ksh93 seems to ignore the numbered conversions when counting > the args for the unnumbered ones (so "A C B" (for the first line anyway, > I won't go on about repeating the format string again). > > The previous version made an unnumbered arg conversion use the next arg > after the last one used (which would give "A C D" using a more reasonable > interpretation of %3$). > Yes, since numbered unumbered usage was not define (C libc doesn't allow the mix, doesn't define fmt reuse either) I decided to find a possible way of doing it. Previous attempt of placing unumbered after the last numbered one was leading with serious problem when going into number/unnumbered num.prec. So previous attempt was trying to do for '%3s %s' the %s is next to the third arg then would be equivalent to '%3s %4s', this lead to all sort of bug and crash and then was never used. The new semantic is simple - numbered are indexed args access (easy to understand) - unumbered are counting only the unumbered from the fmt string This way when you don't mix then the both work as expected. When you mix them, you need a little head scratch, it is useless, but predictable and unbreakable. Since nothing worked before i.e all shell either crashed or refused to run so complicated construct, then doing this didn't break anything, just makes numbered working, not breaking unumbered. Now the dare devil can still mix'n'match, it may not produce what they would like, but at least it don't crash, and produce result as announced for this semantic. Again other semantic can be done for mix'n'match... I would vote for refusing mix'n'match altogeher, yet this is not what I've done for ksh93 because though bugged it was still defined and one could ask for fix > > > printf '%s %s %s %3$s %s\n' A B C D > $ printf '%s %s %s %3$s %s\n' A B C D A B C C D Easy to predict 4 %s take in that order and one number that access the indexed one, no surprise > > > printf '%s %$4s %s %s %s' A B C D > $ printf '%s %$4s %s %s %s' A B C D A /d1/ksh-latest/arch/linux.i386-64/bin/ksh: printf: $: unknown format specifier I guess you meant $ printf '%s %4$s %s %s %s' A B C D A D B C D Can't blame the syntax error :-) I am dislexic too again no surprise here the %s are counted sequentially and the indexed is find directly. The more interesting is $ printf '%s %6$s %s %s %s' A B C D A B C D The 6th does't exist so get '' Again simple rule of thumb if you don't mix'n'match they all works as expected, if you insist on mix'n'match you are entering someting that has never worked before, and then you got to test do decide how to mix'n'match > > | It's worse -- even if a format string using only numbered conversions > | doesn't consume all the arguments, as long as it consumes the last one, > | the format string doesn't get reused. It all depends on whatever > peculiar > | definition of "satisfy" you use. > > Yes, which is where the trick of including a conversion "%999$.0s" in the > format string is supposed to stop format string reuse -- as long as there > are > no more than 999 args given of course. This issue has nothing to do with > the > mixed numbered/unnumbered problem, which rightly should just be > unspecified, > and implementations do whatever they like, reasonable or not (as in the eye > of the coder), but that format string reuse is simply wrong in the numbered > conversion case, no-one really needs that. > > Again the rule I used for ksh93 is that the next arg for fmt reuse is max( number_of_unumbered_occurences, highest_numberd_index ) A simple rule easy to understand, and making non mixed mode to work as expected, again leaving mixed mode in the complexity of counting things. On top of the fact those rules are simple, they also ease the fmt scan and arg fetching. Another way of saing all this is that %s (unnumbered) are in fact internally numbered with 'seq' so %s %s in internally %(seq++)s %(seq++)s and then numbered are in the midle of this %(seq++)s %4s %(seq++s) Next fmt skip max(seq,4) I forgot to mention your trick to nuke the fmt reuse still works $ printf '%s %s %s %999$s' A B C D E F G A B C :-) Cheers
