Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

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

by ikegami (Pope)
on Jul 21, 2009 at 21:01 UTC ( #782078=note: print w/ replies, xml ) Need Help??


in reply to How do I quickly strip blank space from the beginning/end of a string?

Your solutions are very broken.

  • All of your solutions require the last non-space character to be an uppercase letter. You could say you're investigating a subset of the original question, except that your input has no uppercase letters. Use \s or a space instead of [^A-Z]. Use \S instead of [A-Z].

  • Some of your solutions have problems with trailing newlines due to the missing "s" modifier. /./ doesn't match newlines without it.

  • All but the last of your solutions don't work if the input is made entirely of spaces.

There's also a issue with your benchmark. Benchmarking code that removes trailing spaces when your input never has trailing spaces is odd. Include a case where the input has trailing spaces!


Comment on Re: How do I quickly strip blank space from the beginning/end of a string?
Select or Download Code
Replies are listed 'Best First'.
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
    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

      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?

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://782078]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others perusing the Monastery: (11)
As of 2015-07-29 08:38 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (262 votes), past polls