From: Robert Klemme <shortcutter@...>
Date: 2008-11-13T05:27:27+09:00
Subject: Re: Ruby Sub Regular Expression

On 12.11.2008 17:14, Jesús Gabriel y Galán wrote:
> On Wed, Nov 12, 2008 at 4:52 PM, Dave Roberts <dave.a.roberts@gmail.com> wrote:
>> Hello!  I have a string: "Hello - 1 - World"
>>
>> irb(main):017:0> a = "Hello - 1 - World"
>> => "Hello - 1 - World"
>>
>> I want to chop off the "Hello - " part.  Hello could be any word, so I
>> want to match it generically.
>> To match the first minus I do this:
>>
>> irb(main):018:0> b = a.sub(/\s-\s/, "")
>> => "Hello1 - World"
>>
>> Good!  Now to get rid of the first word I try this:
>>
>> irb(main):019:0> c = a.sub(/.*\s-\s/, "")
>> => "World"
>>
>> Bad!  It matched to the second minus!  Why does sub do this?  I thought
>> it was supposed to match the first occurrence only.
> 
> Because * by default is greedy, so it tries to match as much as it can.
> Try this:
> 
> irb(main):002:0> c = a.sub(/.*?\s-\s/, "")
> => "1 - World"

Other variants would be

irb(main):001:0> a = "Hello - 1 - World"
=> "Hello - 1 - World"
irb(main):002:0> a[/\d+\s+-.*/]
=> "1 - World"
irb(main):003:0> a.sub /^\S+\s+-\s+/, ''
=> "1 - World"
irb(main):004:0> a.sub /^\w+\s+-\s+/, ''
=> "1 - World"
irb(main):005:0>

Cheers

	robert