From: Morton Goldberg <m_goldberg@...>
Date: 2007-07-20T14:01:54+09:00
Subject: Re: Is there a replacement for sub?

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