compile-time regex redux

[Walter Bright]

Andrei Alexandrescu (See Website For Email) wrote:
> Walter Bright wrote:
>> But I think we now have good reasons to revisit this, at least for 
>> compile time use only. For example:
>>
>>     ("aa|b" ~~ "ababb") would evaluate to "ab"
>>
>> I expect one would generally only see this kind of thing inside 
>> templates, not user code.
> 
> The more traditional way is to mention the string first and pattern 
> second, so:
> 
> ("ababb" ~~ "aa|b") // match this guy against this pattern
> 
> And I think it returns "b" - juxtaposition has a higher priority than 
> "|", so your pattern is "either two a's or one b". :o)

My bad. Some more things to think about:

1) Returning the left match, the match, the right match?
2) Returning values of parenthesized expressions?
3) Some sort of sed-like replacement syntax?

An alternative is to have the compiler recognize std.Regexp names as 
being built-in.