# Compare to strings

**URL:** <https://www.ruby-forum.com/t/compare-to-strings/93594>\
**Category:** Ruby\
**Created:** [April 5, 2006, 12:28am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594 "2006-04-05T00:28:15Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 5, 2006, 12:28am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/1 "2006-04-05T00:28:15Z")

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Hello,

What is the best approach to searching a string for another string?

For instance, I have:

url1 = ‘[http://www.url.com](http://www.url.com)’  
url2 = ‘[http://www.url.com/page](http://www.url.com/page)’

If part of url1 is in url2, like above, I’d like to declare it a  
match. I’m sure this happens using a regular expression, but my  
experience is limited with them.

The other problem is that I’m not going to be looking for just one  
url1, but I have an entire database table full of those to compare to  
an entire database table of url2.

Any thoughts on approaching this problem are appreciated.

Thanks  
Clint

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 5, 2006, 4:12am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/2 "2006-04-05T04:12:58Z")

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On 4/4/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > url1 = ‘[http://www.url.com](http://www.url.com)’  
> > Any thoughts on approaching this problem are appreciated.  
> > David A. Black (removed\_email\_address@domain.invalid)  
> > Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))
> 
> “Ruby for Rails” chapters now available  
> from Manning Early Access Program! [Ruby for Rails](http://www.manning.com/books/black)

I can’t think of why that wouldn’t work. Thank you.

Clint

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 5, 2006, 2:39am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/3 "2006-04-05T02:39:03Z")

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Hi –

On Wed, 5 Apr 2006, Clint P. wrote:

> match. I’m sure this happens using a regular expression, but my  
> experience is limited with them.
> 
> The other problem is that I’m not going to be looking for just one  
> url1, but I have an entire database table full of those to compare to  
> an entire database table of url2.
> 
> Any thoughts on approaching this problem are appreciated.

It’s not a complete answer, but in case it helps: String has an  
include? method:

url2.include?(url1) =\> true

David

–  
David A. Black (removed\_email\_address@domain.invalid)  
Ruby Power and Light, LLC ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))

“Ruby for Rails” chapters now available  
from Manning Early Access Program! [Ruby for Rails](http://www.manning.com/books/black)

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 6, 2006, 1:24am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/4 "2006-04-06T01:24:00Z")

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> ```
> x.report{ 100000.times { url2.include?( url ) } }
> 
> user system total real
> 
> ```
> 
> Zach

Excellent info Zach. Very relevant for me. I’ll have thousands of  
links to do this with.

Thanks again,  
Clint

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 5, 2006, 8:49am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/5 "2006-04-05T08:49:51Z")

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removed\_email\_address@domain.invalid wrote:

> > url1 = ‘[http://www.url.com](http://www.url.com)’  
> > Any thoughts on approaching this problem are appreciated.
> 
> It’s not a complete answer, but in case it helps: String has an  
> include? method:
> 
> url2.include?(url1) =\> true

Using String#include? is much faster then regexp matching. Here are some  
benchmarks. I didn’t test this with Oniguruma though, but I su

– START CODE –  
require ‘benchmark’

url = “[http://www.url.com/](http://www.url.com/)”  
url2 = “[http://www.url.com/page](http://www.url.com/page)”

Benchmark.bm{ |x|  
x.report{ 100000.times { url2.include?( url ) } }  
x.report{ 100000.times { url2 =~ /#{url}/ } }  
}  
– END CODE —

Benchmark Windows ruby 1.8.4 (2005-12-24) [i386-mswin32]  
C:\source\projects\ruby\strings\>ruby temp.rb  
user system total real  
0.080000 0.000000 0.080000 ( 0.080000)  
1.722000 0.130000 1.852000 ( 1.873000)

Benchmark Linux ruby 1.8.4 (2005-12-24) [i686-linux]  
zdennis@lima:~$ ruby-1.8.4 temp.rb  
user system total real  
0.100000 0.000000 0.100000 ( 0.119403)  
1.570000 0.040000 1.610000 ( 1.760446)

Benchmark Linux ruby 1.8.3 (2005-06-23) [i486-linux]  
zdennis@lima:~$ ruby temp.rb  
user system total real  
0.160000 0.030000 0.190000 ( 0.209436)  
1.720000 0.080000 1.800000 ( 2.021754)

Benchmark Linux ruby 1.8.2 (2005-04-11) [i386-linux]  
zdennis@jboss:~$ ruby temp.rb  
user system total real  
0.000000 0.000000 0.000000 ( 0.246239)  
0.000000 0.000000 0.000000 ( 1.401049)

Zach

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 6, 2006, 2:45am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/6 "2006-04-06T02:45:48Z")

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Hi,

On Thu, 06 Apr 2006 01:23:31 +0200, Clint P.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Excellent info Zach. Very relevant for me. I’ll have thousands of  
> links to do this with.

$ cat str\_inc\_bench.rb  
require ‘benchmark’

url = “[http://www.url.com/](http://www.url.com/)”  
url2 = “[http://www.url.com/page](http://www.url.com/page)”  
urlrx = /#{url}/

Benchmark.bm{ |x|  
x.report{ 100000.times { url2.include?( url ) } }  
x.report{ 100000.times { url2 =~ urlrx } }  
x.report{ 100000.times { url2 =~ /#{url}/ } }  
}  
$ ruby -v str\_inc\_bench.rb  
ruby 1.8.4 (2005-12-24) [i686-linux]  
user system total real  
0.070000 0.000000 0.070000 ( 0.071435)  
0.130000 0.000000 0.130000 ( 0.130016)  
1.130000 0.020000 1.150000 ( 1.182629)

So, regular expression matching itself is not that much slower than  
String#include?.  
What makes “url2 =~ /#{url}/” slow is the creation of so many Regexp  
objects.

I just wanted to point that out.

Dominik

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**Author:** ![pachl](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/5f9b8f/32.png) [@pachl](https://www.ruby-forum.com/u/pachl)\
**Post date:** [April 6, 2006, 3:15am UTC](https://www.ruby-forum.com/t/compare-to-strings/93594/7 "2006-04-06T03:15:55Z")

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On 4/5/06, Dominik B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> So, regular expression matching itself is not that much slower than  
> String#include?.  
> What makes “url2 =~ /#{url}/” slow is the creation of so many Regexp  
> objects.

Ruby has some very subtle optimizations for Regexps too:

# ruby 1.8.4 (2006-03-20) [powerpc-darwin8.5.0]

GC.disable  
n = ObjectSpace.each\_object(Regexp){}  
def foo; /abc/ end

# Note I didn’t call foo.

ObjectSpace.each\_object(Regexp){} - n #=\> 1  
1000.times {foo}  
ObjectSpace.each\_object(Regexp){} - n #=\> 1

It is always nice to see simple optimizations like this.

Brian.