From: Todd Benson <caduceass@...>
Date: 2008-04-13T01:03:36+09:00
Subject: Re: surprise in sub

On Sat, Apr 12, 2008 at 9:25 AM, Christopher Dicely <cmdicely@gmail.com> wrote:
> On Fri, Apr 11, 2008 at 9:20 AM, matt neuburg <matt@tidbits.com> wrote:
>  > irb(main):001:0> s = "\\\\"
>  >  => "\\\\"
>  >  irb(main):002:0> s.length
>  >  => 2
>  >  irb(main):003:0> s = "howdy".sub("howdy", s)
>  >  => "\\"
>  >  irb(main):004:0> s.length
>  >  => 1
>  >
>
> >  So merely using a string as the second param of sub (the replacement
>  >  value) can cause that string to be altered.
>
>  Nope, using the string (s) as the second parameter of sub did nothing to alter
>  it. This is clear if you use a different variable as the assignment target:
>
>
>
>  irb(main):001:0> s='\\\\'
>  => "\\\\"
>  irb(main):002:0> s.length
>  => 2
>  irb(main):003:0> foo = "howdy".sub("howdy",s)
>
> => "\\"
>  irb(main):004:0> s
>  => "\\\\"
>  irb(main):005:0> s.length
>  => 2
>  irb(main):006:0> foo
>  => "\\"
>  irb(main):007:0> foo.length
>  => 1
>
>  s isn't changed by being used as the second argument to sub, instead, the
>  string sent as the second argument to sub is processed for escape sequences
>  so that the substring '\\'  occurring in that string is treated as a
>  single literal '\'
>  when used in the replacement.
>
>  But its not changed, as the above irb session shows. s is unmodified.

When I first read the post, I immediately wanted to strike out with a
"well, you're assigning" response.

I'm not sure, but I think the OP was referring to what you said;
namely, how the escaping happens before subbing.

Todd