From: Robert Feldt <feldt@...>
Date: 2004-04-07T07:29:48+09:00
Subject: Re: Bug in sub?

Ara.T.Howard wrote:

>>Sorry, call me thick but I don't understand that :-)
>>
>>Did Guy confirm that it was a bug, or show that it is not a bug?
>>    
>>
>
> __not_a_bug__ # that's python for not a bug
>
>
>svg% ruby -e 'p "abcdef".sub(/(.)./, "\\+")'
>"acdef"
>svg%
>
>
>  /(.)./ and '\+'
>
>    - match a char, followed by another char. remember the first char
>    - replace the entire match with the remembered first char
>
>    abcdef -> acdef
>    --         
>    -         -
>
>svg% ruby -e 'p "abcdef".sub(/(.).(..)/, "\\+")'
>"cdef"
>svg% 
>
>
>  /(.).(..)/ and '\+'
>
>    - match a char, followed by another char. followed by two more chars.
>      remember the last two chars (and the first) 
>    - replace the entire match with the remembered last two chars  (which is
>      the 'last matched group')
>
>    abcdef -> cdef
>    ----        
>      --      --
>
>
>  
>
Yes, and further: If you want to do substitutions and aren't sure there 
will be no backslash sequences in the replacement string you should use 
the block form, like so:

$ ruby -e 'p "a".sub("a") {"\\+"}'
"\\+"

I added a note to my code review checklist to "always" use the block 
form... ;)

Sorry for wasting bandwidth on this; I should have read the docs more 
closely.

/Robert