From: x17y19 <amberarrow@...>
Date: 2008-04-12T03:15:04+09:00
Subject: Re: surprise in sub

On Apr 11, 9:15 am, m...@tidbits.com (matt neuburg) 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.
>
> Now, the documentation does "warn" that sequences \1, \2 etc. are valid
> in the replacement string. This suggests that the replacement string is
> processed before use; to be sure, it says nothing about "\\" explicitly,
> but I do see of course that one must deal with "\\" in order to escape
> the escaping. Furthermore, there's a "workaround", namely to write the
> third line as follows:
>
> s = "howdy".sub("howdy") {|x| s}
>
> Still, I got seriously caught by this behavior and it was tricky to
> track down. m.
>
> --
> matt neuburg, phd = m...@tidbits.com,http://www.tidbits.com/matt/
> Leopard -http://www.takecontrolbooks.com/leopard-customizing.html
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s is changing because you assigned to it, not because of using it
as the second parameter of sub(). Try assigning the result to a
different variable like so:

ss = "howdy".sub("howdy", s)