Rails - Jun 2009 - performance improvement in method to strip non-numeral characters from string ??

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

On Jun 23, 6:37 pm, Vipin
<sh.vi...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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
> 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

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/), or purchased from
Pragmatic Programmers (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 Groups 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 Jones

On Jun 23, 1:37 pm, Vipin
<sh.vi...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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
>
> 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

On Jun 24, 9:18 pm, Matt Jones
<al2o...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> 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/), or purchased from
> Pragmatic Programmers (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 Groups 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 Jones
>
> On Jun 23, 1:37 pm, Vipin
<sh.vi...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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
>
> > 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
Thanks for advice, Matt. I would like to read that book as soon as i
get the time from current project.
Thanks
vipin