Splitting Hairs [tangent to: Splitting in while loop]

If you just print an array (as in print @_) there will be nothing to show where each element starts and ends

Technically, there will be something: the value of the special variable $, -- it just happens that it defaults to undef (‡) so the separator used is nothing when printed. But if you change or localize its value to a different value, there will be a separator, without having to stringify the array first.

I wouldn't have mentioned this, but you went on to encourage the use of $" and interpolating the array in a string. If all you are doing is trying to get a separator for printing an array or other list (˛), then $, will work without having to interpolate/stringify.

-- pryrt

‡: ... and apparently ignores use warnings 'uninitialized';: gotta love magic variables.

˛: However, $, applies to everything when printing in list context, so local $,=',';print $a, @_, $b will have more separator instances than local $,=undef; local $"=','; print $a, "@_", $b; -- which may or may not be what you want.

ł: Also, $, is much easier to use in a Windows cmd.exe one-liner than $". As a workaround, use English to the rescue:

C:\usr\local\share>perl -MEnglish -wle "@_ = qw{a bcd ef}; print qq(@_
+); local $LIST_SEPARATOR=','; print qq(@_)"
a bcd ef
a,bcd,ef
[download]

Comment on Splitting Hairs [tangent to: Splitting in while loop] Select or Download Code

Replies are listed 'Best First'.
Re: Splitting Hairs [tangent to: Splitting in while loop] by kcott (Archbishop) on Oct 08, 2021 at 19:20 UTC
G'day pryrt, That must be an extremely sharp, obsidian-bladed, cutting implement that you're using to split such a fine hair. I applaud your hairdressing skills. 💈 💇 👏 "I wouldn't have mentioned this, ..." I've no problem with you mentioning special variables, especially the less commonly used ones. In my opinion, the more exposure they get the better. "... but you went on to encourage the use of $" and interpolating the array in a string." I would not say that offering an option that could be used in "rare situations" qualifies as encouraging such usage. "If all you are doing is trying to get a separator ... then $, will work without having to interpolate/stringify." Let's see how that pans out. The default for `$"` is `' '` so, except in "rare situations", there would be no need to localise a new value. The default for `$,` is `undef` so, in most situations, there is a need to localise a new value. # A simple scenario printing a named array: $ perl -e 'my @x = qw{a bcd ef}; print "@x\n"' a bcd ef $ perl -e 'my @x = qw{a bcd ef}; { local $, = ","; print @x, "\n" }' a,bcd,ef, # Oops! Bogus comma at the end. Better split the print list. $ perl -e 'my @x = qw{a bcd ef}; { local $, = ","; print @x; print "\n +" }' a,bcd,ef # A more complex scenario printing an expression which evaluates to a +list: $ perl -e 'print "@{[f()]}\n"; sub f { qw{a bcd ef} }' a bcd ef $ perl -e '{ local $, = ","; print f(), "\n"; } sub f { qw{a bcd ef} } +' a,bcd,ef, # Oops! Bogus comma at the end. Better split the print list. $ perl -e '{ local $, = ","; print f(); print "\n"; } sub f { qw{a bcd + ef} }' a,bcd,ef [download] Notes: I discovered the "Oops!" while testing the one-liner examples. I included it because it would appear to be an easily overlooked gotcha. I was using the '`@{[...]}`' idiom long before I knew it had a name or that perlsecret even existed. For those interested, see "perlsecret: Baby cart". Based on the results above, I will continue to put arrays in interpolating quotes when I print them. That not a recommendation; just what I'll be doing; everyone is free to make their own choices. — Ken	[reply] [d/l] [select]
Re^2: Splitting Hairs [tangent to: Splitting in while loop] by eyepopslikeamosquito (Archbishop) on Oct 08, 2021 at 23:53 UTC
I was using the `'@{[...]}'` idiom long before I knew it had a name or that perlsecret even existed You're in good company! When merlyn invented this idiom back in 1994, he regretted not asking Larry's daughter Heidi to name it, after her previous spectacular success in coining the `<=>` spaceship operator name. Actually, I see just now there's a bug in perlsecret in that it attributes the naming of the spaceship operator to Randal Schwartz when the true credit belongs to Larry's daughter Heidi according to the man himself! For the long and fascinating history behind the naming of the `@{[...]}` "baby cart" secret operator see: Re^3: Hidden features of Perl (Baby Cart Secret Operator)	[reply] [d/l] [select]
Re^3: Splitting Hairs [tangent to: Splitting in while loop] by kcott (Archbishop) on Oct 09, 2021 at 03:11 UTC
There are others (e.g. `!!` and `0+`) which I use regularly but rarely recognise as secret operators and, even if I do, their names often allude me. In contrast, there's an infamous one which is impossible to unsee and, therefore, impossible to forget. I've not named it on purpose: in the hope that I may have saved at least some from mental trauma. :-) — Ken	[reply] [d/l] [select]
Re^3: Splitting Hairs [tangent to: Splitting in while loop] by LanX (Saint) on Oct 09, 2021 at 00:32 UTC
did anyone ever suggest just a mundane "code interpolation" ? Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery} Update: corrected `s/profane/mundane/` (false friend)	[reply] [d/l]
Re^4: Splitting Hairs [tangent to: Splitting in while loop] by eyepopslikeamosquito (Archbishop) on Oct 09, 2021 at 00:44 UTC
Re^5: Splitting Hairs (Mexican Sledge) by LanX (Saint) on Oct 09, 2021 at 11:54 UTC
Some notes below your chosen depth have not been shown here
Re: Splitting Hairs [tangent to: Splitting in while loop] by LanX (Saint) on Oct 08, 2021 at 14:28 UTC
> `‡ ... ˛ ... ł ...` [download] /me .oO( glad to see people infected with FoViD ° ;-) Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery} °) Footnote Virus Disease ....	[reply] [d/l]