From: Jens Wille <jens.wille@...>
Date: 2008-04-03T06:13:54+09:00
Subject: Re: confused by 'test'.gsub(/.*/,'x')

Thomas Wieczorek [2008-04-02 22:59]:
> On Wed, Apr 2, 2008 at 10:55 PM, Yossef Mendelssohn
> <ymendel@pobox.com> wrote:
>> On Apr 2, 3:35 pm, "Thomas Wieczorek"
>> <wieczo...@googlemail.com> wrote:
>>> .* matches NO and ALL characters, so gsub() substitutes 
>>> ''(empty)(=>'x') and and 'test'(=>'x') with x, so you get
>>> 'xx'
>> That sounds like an explanation why ''.gsub(/.*/, 'x') is 'x'
>> more than why 'test'.gsub(/.*/, 'x') is 'xx'. It seems to me
>> that the .* should match [empty string]test[empty string] just once.
> Yeah, it is confusing me, but I agreed on that explanation with
> myself, when I read it once here. I'd also expect 'x' instead of 'xx'
can't explain it either, i'm afraid. but you can see what it does
like so:

irb> 'test'.gsub(/.*/) { |m| p m; 'x'}
"test"
""
=>"xx"

as soon as you anchor the regexp at the beginning of the string it
gives the expected result:

irb> 'test'.gsub(/\A.*/) { |m| p m; 'x'}
"test"
=>"x"

or just do:

irb> 'test'.sub(/.*/) { |m| p m; 'x'}
"test"
=>"x"

;-)

cheers
jens