# Performance improvement in method to strip non-numeral characters from string?

**URL:** <https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867>\
**Category:** Rails\
**Created:** [June 23, 2009, 7:38pm UTC](https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867 "2009-06-23T19:38:31Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Vipin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/edb3f5/32.png) [@Vipin](https://www.ruby-forum.com/u/Vipin)\
**Post date:** [June 23, 2009, 7:38pm UTC](https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867/1 "2009-06-23T19:38:31Z")

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I need to write a method such that when we pass on a string to it, it  
returns a substring out of it. returned string is such that it  
consists of numerals only. All the characters other than numerals are  
stripped away.

e.g.  
" 2009-05-30 10:25:15 UTC" ==\> 20090530102515

I have written the following method for the same.  
It seems to be working but I am looking for your suggestions /  
feedback for  
–\> performance improvment  
–\> any bug that i am not able to see

def getNumeralString(istr)  
x = istr.split(//)  
istr = “”  
x.each{|a|  
if a[0] \>= ‘0’[0] && a[0] \<= ‘9’[0]  
istr = istr +a  
end  
};  
return istr  
end

Thanks for feedback

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<div class="post-metadata">

**Author:** ![Vipin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/edb3f5/32.png) [@Vipin](https://www.ruby-forum.com/u/Vipin)\
**Post date:** [June 23, 2009, 8:22pm UTC](https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867/2 "2009-06-23T20:22:36Z")

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On Jun 23, 6:37 pm, Vipin [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> I need to write a method such that when we pass on a string to it, it  
> returns a substring out of it. returned string is such that it  
> consists of numerals only. All the characters other than numerals are  
> stripped away.
> 
> e.g.  
> " 2009-05-30 10:25:15 UTC" ==\> 20090530102515

s.gsub(/[^0-9]/,‘’)

is more concise and probably faster

Fred

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<div class="post-metadata">

**Author:** ![Vipin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/edb3f5/32.png) [@Vipin](https://www.ruby-forum.com/u/Vipin)\
**Post date:** [June 24, 2009, 6:19pm UTC](https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867/3 "2009-06-24T18:19:03Z")

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I think Fred’s nailed the solution already, but some more general  
advice:

- I’d _highly_ recommend you read Programming Ruby (the Pickaxe book),  
either online ([http://www.rubycentral.com/book/](http://www.rubycentral.com/book/)), or purchased from  
Pragmatic Programmers ([Pragmatic Bookshelf: By Developers, For Developers](http://www.pragprog.com/titles/ruby/programming-)  
ruby). Your original code looks like a classic example of “C  
programmers can program any language in C”, and learning the Ruby  
idioms will help avoid this sort of thing.

- I’d also recommend that you work on relaxing your “speed optimizing”  
tendencies. Skimming through some of your other posts to various  
Google G. shows quite a few discussions most would describe as  
“premature optimization”. While it’s important to be a little  
concerned about performance (ie, not writing algorithms that are  
deliberately inefficient), it’s equally destructive to be too  
concerned about performance. At least at the outset, just write clear  
code. A surprising amount of the time in Ruby, clear code (Fred’s  
solution using gsub) is significantly faster than unclear code.

–Matt J.

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<div class="post-metadata">

**Author:** ![Vipin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/edb3f5/32.png) [@Vipin](https://www.ruby-forum.com/u/Vipin)\
**Post date:** [June 26, 2009, 3:18am UTC](https://www.ruby-forum.com/t/performance-improvement-in-method-to-strip-non-numeral-characters-from-string/170867/4 "2009-06-26T03:18:56Z")

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On Jun 24, 9:18 pm, Matt J. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> - I’d also recommend that you work on relaxing your “speed optimizing”
> 
> > I have written the following method for the same.  
> > istr = istr +a  
> > end  
> > };  
> > return istr  
> > end
> 
> > Thanks for feedback

Thanks for advice, Matt. I would like to read that book as soon as i  
get the time from current project.  
Thanks  
vipin