From: dblack@...
Date: 2006-07-06T02:50:11+09:00
Subject: Re: Find Position of text

Hi --

On Thu, 6 Jul 2006, j3n7il jones wrote:

> Im trying to recreate a function I had in Delphi for ruby, but cannot
> figure out how to search for a string withn a string
>
> Here is the Delphi code
>
> function ReplaceString(str, value, replacer: String): String;
> var
>  aPos: Integer;
>  rslt: String;
> begin
>  aPos := Pos(value, str);
>  rslt := '';
>  result := str;//in case there is nothing to replace, return orig
> string
>  while (aPos <> 0) do begin
>    rslt := Copy(str, 1, aPos - 1) + replacer;
>    rslt := rslt + Copy(str, aPos + Length(value), Length(str));
>    str := rslt;
>    aPos := Pos(value, str);
>    result := rslt;
>  end;
> end;
>
> As you can see after begin, it calls a pascal function called "pos"
>
> which just looks for value(a string) within str (another string) and
> returns a number, the position of value within str.
>
> Possible in ruby?

Of course -- and there's even a built-in method that does it :-)
Actually a couple of them.  Check out String#index and String#rindex.

   str = "This is a string."
   str.index("is")   # 2
   str.rindex("is")  # 5 (i.e., last occurence)
   str.index(/i./)   # 2 (using regex)

The =~ method/operator also returns an index.


David

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