Re: How to split a string into chunks of length n or less

Yesterday I had to learn that string operations might be more efficient. So here we go:

my $x = "0123456789abcdef" x 4 . "XXX";
my $chunksize= 16;
for (my $i=$chunksize*int((length($x)-1)/$chunksize);$i;$i-=$chunksize
+) {
    substr($x,$i,0)=" ";
};
print $x;
[download]

~~And if you really want to use split~~ Or you might still want a regular expression:

join " ",$x=~/(.{1,$chunksize})/g
[download]

Update to my first codesnippet: Thanks to oshalla's comment above I noticed that I also had a space too much when the string has a length being a multiple of chunksize.

s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e

Comment on Re: How to split a string into chunks of length n or less Select or Download Code

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Re^2: How to split a string into chunks of length n or less by moritz (Cardinal) on Aug 21, 2008 at 17:04 UTC
I wrote a small benchmark, under the assumption that the implementation is not allowed to modify the original string, and if it does it has to take a copy first. I found out that all versions are extremely fast, and thus not easy to benchmark. So probably my benchmark is flawed, take it with a grain of salt. Read more... (1148 Bytes) Here are the results (with perl5.10.0): `Rate readl subst unpack substr readl 78783885/s -- -17% -18% -24% subst 95302528/s 21% -- -1% -8% unpack 96105165/s 22% 1% -- -8% substr 103929656/s 32% 9% 8% --` [download] And then I ran it again: `Rate subst readl substr unpack subst 81695687/s -- -1% -36% -65% readl 82899185/s 1% -- -35% -65% substr 128382089/s 57% 55% -- -46% unpack 235800076/s 189% 184% 84% --` [download] and thought "WTF?" I increased the length of the source string by a factor of 100, and started the benchmark again. It still runs (after about 15 minutes). My conclusions are that the differences are so small (or my benchmark so flawed...) that you can basically neglect them.	[reply] [d/l] [select]
Re^3: How to split a string into chunks of length n or less by Skeeve (Parson) on Aug 21, 2008 at 17:09 UTC
You missed the corrections some have added. There is still the extra space at the end in certain cases. See oshalla's post and my update above. I added my second code snippet and ran this: Read more... (1270 Bytes) My results: `Rate unpack substr subst re readl unpack 29656695/s -- -5% -8% -14% -16% substr 31367657/s 6% -- -3% -9% -11% subst 32410531/s 9% 3% -- -6% -8% re 34622792/s 17% 10% 7% -- -2% readl 35251272/s 19% 12% 9% 2% --` [download] `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]