How to split_and_pad string to n-th chars pieces with one regular expression?

bdimych has asked for the wisdom of the Perl Monks concerning the following question:

Hi All. I need to split the string to a several substrings of the same length, the last substring should be blank padded so that it's length also would be the same. And - that's the problem - the string may be empty also.

That is what I've written
1) - ok on empty string, but on not empty string produce unnecessary blank substring

my $x = "";
$x=~s/(.{0,3})/"'$1".(' 'x(3-length($1)))."'\n"/eg;
print $x
---
'   '


my $x = "1234567890";
$x=~s/(.{0,3})/"'$1".(' 'x(3-length($1)))."'\n"/eg;
print $x
---
'123'
'456'
'789'
'0  '
'   '
[download]

2) - ok on not empty string, but empty string is not padded

my $x = "";
$x=~s/(.{1,3})/"'$1".(' 'x(3-length($1)))."'\n"/eg;
print $x
---
___prints_nothing___


my $x = "1234567890";
$x=~s/(.{1,3})/"'$1".(' 'x(3-length($1)))."'\n"/eg;
print $x
---
'123'
'456'
'789'
'0  '
[download]

any advice?

Comment on How to split_and_pad string to n-th chars pieces with one regular expression? Select or Download Code

Replies are listed 'Best First'.
Re: How to split_and_pad string to n-th chars pieces with one regular expression? by BrowserUk (Patriarch) on Nov 30, 2007 at 14:27 UTC
If you must, this seems to work. `$x =~ s[(.{0,3}\|)]["'$1" . (' ' x (3-length($1))) ."'\n"]ge;` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re: How to split_and_pad string to n-th chars pieces with one regular expression? by Limbic~Region (Chancellor) on Nov 30, 2007 at 14:19 UTC
bdimych, any advice? Yes - stop trying to do this in a single regular expression. While I am sure there will be a dozen correct and working solutions provided, I doubt any will be self-documenting. I also suspect anyone maintaining your code will take pause when they come across it. Why not come up with a split_by_n() function where you can pass in a string and a length and get back what you want. Heck, you could then have optional parameters for what to do with empty strings, padding or not, etc. Cheers - L~R	[reply]
Re: How to split_and_pad string to n-th chars pieces with one regular expression? by mwah (Hermit) on Nov 30, 2007 at 14:40 UTC
Maybe I misunderstood the problem, but I'd try: ~~`$txt =~ s/(.{1,3})/sprintf"%03s\n",$1/ge;`~~ Update: missed the "empty string" part: `... $txt =~ s/(.{1,3}\|^$)/sprintf"'%3s'\n",$1/ge; print $txt; ...` [download] Regards mwa	[reply] [d/l] [select]
Re: How to split_and_pad string to n-th chars pieces with one regular expression? by bdimych (Monk) on Nov 30, 2007 at 15:00 UTC
many thanks, it is solved, If combine BrowserUk's and mwah's solutions, then it works fine `$x=~s/(.{1,3}\|^$)\n?/sprintf"'%-3s'\n",$1/eg;` [download] it works even on multiline strings --- and even multiline with emptyline mixed together `$x=~s/(.{1,3}\|^$)\n?/sprintf"'%-3s'\n",$1/meg;` [download]	[reply] [d/l] [select]


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