Re: [Help-smalltalk] [poll] regex literals

[Paolo Bonzini]

Tony Garnock-Jones wrote:
> Paolo Bonzini wrote:
> > I'm thinking of adding regex literals to GNU Smalltalk.
>
> I'd be against this.
>
>  'a.*b' asRegex
>
> to me seems better, and doesn't require and lexer/parser changes.

It's also slower, which is why as of today 'a.*b' works even without 
sending #asRegex.

However, *always* treating string literals as regexes is going to give 
problems in the long term.  In particular, it would break with another 
extension that I was thinking about:

    #(1 3 2 6 5 4) select: #odd => #(1 3 5)
    #(1 12 2) select: (1 to: 10) => #(1 12)
    #('foo' 'bar') select: ##/f./ => #('foo')

This would be quite easily implemented (#select: would send a new 
message to its argument, e.g. #~, instead of #value:).  If regexes would 
be implemented simply as strings, however, there would be a conflict 
between the Collection example (second) and the regex example (third):

    'foo' select: 'aeiouy' => 'oo'
    #('foo') select: 'f.' => cannot make it return 'foo' as I'd like!

That's why in this case, simply using string literals as regexes 
wouldn't work.  You would need to specify #asRegex to get the desired 
behavior.

As I said, I'm also thinking "no"/"not yet".  It's not paramount: older 
code would be unaffected, and I could start implementing the above 
(which is not happening any time soon), and then see if it is a problem. 
 Just, there *might* be one.

Paolo