Re: Re: Questions: Roadmap, Publicity/Groovy, Regexps

OK, so it would all be about performance? I imagined the reason to want 
regexps in the language might be to have static typing support, like:

   (x,y) = "123-4567" ~ /\(.*\)-\(.*\)/

That is, the compiler sees in the regexp that there are two groups, and so the 
matching expression returns a couple.

> total = 0
> match_expression = Regexp.new("[a-df-h][aeiou]{2}")
> File.open( 'words', 'r' ) { |file|
>     file.each_line { |line|
>         word = line.chomp
>         total +=1 if word =~ match_expression
>     }  }    puts total
> 
> Well that is perhaps more difficult to read, on the other hand if the 
> match_expression variable has a name that indicates what the expression 
> is then perhaps it is easier to read. The main point about having first 
> class regular expressions is that they get instantiated exactly once and 
> you don't have to worry about making sure they get instanced only once 
> by making them a class wide field (read static data member in C++) or 
> whatever. It's about making it easier for the programmer.

So I guess a regexp gets compiled once per syntactic appearance in the source, 
right? What if the regexp creation method simply used caching? That should get 
you equivalent performance.

In a compiled language, you can actually consider generating the matcher at 
compile time (provided the regexp is known), if you have language support. The 
question is, is there a strong demand for regexp support in Nice? Otherwise, 
what I can see as a more generic enhancement, in the future, is support for 
macros/templates/staged compilation, which would be a way to make it possible 
to implement such features, and others, without hard-wiring them in the 
compiler. I know Bryn Keller has given some thought to this, maybe he will 
comment.

Daniel


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