From: 7stud -- <bbxx789_05ss@...>
Date: 2009-04-29T23:57:17+09:00
Subject: Re: Issue with regexp pattern matcher withing String#gsub

Craig Jolicoeur wrote:
> 7stud -- wrote:
>> ...and that means the error message you posted can't occur.   When I run 
>> the code:
>> 
>>     str = %q{src="/foo/bar.png"}
>> 
>>     str.gsub!( /src=(["'])\S+\?\d*\1/ ) { |s| s.split('?').first + $1 }
>> 
>> there are no errors and no output.  So you must have done something 
>> differently in your code.
> 
> you don't get an error because your initial quote doesnt make the match.
> 

I used the string you provided.  Generally, if you want relevant help, 
you should post relevant data.

>> The side effect of String#split is changing the value of $1.
> 
> It doesn't in ruby 1.8.6:
> 

/(.)/ =~ "abc"
puts $1

"acb".split(" ")
puts $1

--output:--
a
a

> It will if the split is done on a Regexp (but the OP wasn't doing that)
> 
> irb(main):008:0> /(.)/ =~ "abc"; puts $1; "a b".split(/ /); puts $1
> a
> nil

My tests show that every string but " " causes split() to change the 
value of $1.  The docs say that if the pattern given to split() is a 
single space, the string will be split on whitespace with runs of 
whitespace ignored, for example:

result = "a       b".split(" ")
p result

--output:--
["a", "b"]

So a string containing a single space is treated differently than other 
strings by split().  Why that would cause a different result for the 
value of $1, I have no idea.


> ahh, interesting.  thanks so much.  I didn't realize that #split would 
> overwrite those [global variables].
> 
> What exactly does the split function set them to?

"abcd" =~ /a(b)(c)d/
puts $~, $1, $2

--output:--
abcd
b
c

#same program:
"AAAxyzBBB".split(/x(y)z/)
puts $~, $1, $2

--output:--
nil
nil
nil

$1 is supposed to be the string that matches the first grouping of a 
successful match







-- 
Posted via http://www.ruby-forum.com/.