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### Re^2: How do I quickly strip blank space from the beginning/end of a string?

by blahblahblah (Priest)
 on Jul 21, 2009 at 22:25 UTC ( #782109=note: print w/replies, xml ) Need Help??

You're right, in my haste to get this question out there I made the jump from my original problem to japhy's post to talking about his benchmarks. One of my coworkers pointed out the same thing to me as I was headed out the door. Obviously I should be benchmarking the exact problem I want to solve, not some generally similar example. After I get the kids to bed I'll write a better benchmark and try your \K suggestion below too. Thanks.

Also, you made the point that none of my input ends with spaces. I think that's generally true in real life usage too. It's frustrating that we have this pervasive idiom in our code of "strip whitespace just in case", but I think most of the time the input is already just fine. In fact, I think much of the time the input is short and has no spaces at all. I wonder if I should be checking it with index() first to quickly rule out that case.

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Re^3: How do I quickly strip blank space from the beginning/end of a string?
by ikegami (Pope) on Jul 21, 2009 at 23:06 UTC

Also, you made the point that none of my input ends with spaces. I think that's generally true in real life usage too.

Then shouldn't you be benchmarking space detection?

Good point. I've tried the 3 methods below:
if (\$x =~ /\s/)
and
if (substr(\$x, -1) =~ /^\s/
and
if (rindex(\$x," ") == 0 || rindex(\$x,"\r") == 0 || rindex(\$x,"\n") == + 0 || rindex(\$x,"\t") == 0)
The rindex method is much faster on the data that has spaces; otherwise the substr method is the fastest. Any other good ideas, keeping in mind that the data (I think) won't often contain any trailing spaces?

\$x =~ /\s/
doesn't work. It should be
\$x =~ /\s\z/
Bonus: The speed of fixed version won't depend on the length of the string like the broken one did.

if (rindex(\$x," ") == 0 || rindex(\$x,"\r") == 0 || rindex(\$x,"\n") == 0 || rindex(\$x,"\t") == 0)
doesn't work. It should be
if (rindex(\$x," ") == length(\$x)-1 || rindex(\$x,"\n") == length(\$x)-1 || rindex(\$x,"\t") == length(\$x)-1 || rindex(\$x,"\r") == length(\$x)-1)
Or just
my \$ch = substr(\$x, -1); \$ch eq " " || \$ch eq "\n" || \$ch eq "\t" || \$ch eq "\r"

And then there's
length(\$x) && index(" \n\t\r", substr(\$x, -1)) >= 0

You should be concentrating on writing code that actually works before worrying about operations that take 0.00001 second.

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