From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-07-20T16:15:03+09:00
Subject: Re: Is there a replacement for sub?

Morton Goldberg wrote:
> On Jul 19, 2007, at 11:00 PM, Michael W. Ryder wrote:
> 
>> I was trying to come up with a way to remove x instances of a 
>> character from a string and came up with a problem.  If I enter:
>>
>> a = "a b c d e f"
>> for i in 1..3
>>   a = a.sub!(' ', '')
>> end
>> puts a  ==> returns 'abcd e f' which is correct.
>>
>> But if I enter:
>>
>> a = "a b c d e f"
>> for i in 1..10
>>   a = a.sub!(' ', '')
>> end
>> puts a  ==> returns error.rb:3: private method `sub!' called for 
>> nil:NilClass (NoMethodError, and a is now nil.
>>
>> What I am looking for is a way to remove the first n instances of a 
>> blank from the string without wiping out the string if it does not 
>> contain at least n blanks.  I assume there is a way to do this with 
>> regular expressions, but have not found it yet.  This is something an 
>> editor I liked, UCEDIT, on the CDC Cyber had in the 70's.
> 
> How about this?
> 
> n = 3
> "a b c d e f".sub(/(\S\s){#{n}}/) { |m| m.delete(" ") } # => "abcd e f"
> n = 10
> "a b c d e f".sub(/(\S\s){#{n}}/) { |m| m.delete(" ") } # => "a b c d e f"
> 
> Regards, Morton
> 

Is there nothing in regular expressions where you can tell it to do 
something up to n times?