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

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.

update: added paragraph spacing

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

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Re^3: How do I quickly strip blank space from the beginning/end of a string? by ikegami (Patriarch) 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?	[reply] [d/l]
Re^4: How do I quickly strip blank space from the beginning/end of a string? by blahblahblah (Priest) on Jul 22, 2009 at 01:12 UTC
Good point. I've tried the 3 methods below: `if ($x =~ /\s/)` [download] and `if (substr($x, -1) =~ /^\s/` [download] and `if (rindex($x," ") == 0 \|\| rindex($x,"\r") == 0 \|\| rindex($x,"\n") == + 0 \|\| rindex($x,"\t") == 0)` [download] 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?	[reply] [d/l] [select]
Re^5: How do I quickly strip blank space from the beginning/end of a string? by ikegami (Patriarch) on Jul 22, 2009 at 04:22 UTC
`$x =~ /\s/` doesn't work. It should be `$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.	[reply] [d/l] [select]