Andrei Alexandrescu, el 18 de febrero a las 21:35 me escribiste:
> I'm almost done rewriting the regular expression engine, and some pretty
> interesting things have transpired.
>
> First, I separated the engine into two parts, one that is the actual regular
> expression engine, and the other that is the state of the match with some
> particular input. The previous code combined the two into a huge class. The
> engine (written by Walter) translates the regex string into a
> bytecode-compiled
> form. Given that there is a deterministic correspondence between the regex
> string and the bytecode, the Regex engine object is in fact invariant and
> cached by
> the implementation. Caching makes for significant time savings even if e.g.
> the user repeatedly creates a regular expression engine in a loop.
>
> In contrast, the match state depends on the input string. I defined it to
> implement the range interface, so you can either inspect it directly or
> iterate it
> for all matches (if the "g" option was passed to the engine).
>
> The new codebase works with char, wchar, and dchar and any random-access
> range as input (forward ranges to come, and at some point in the future input
> ranges
> as well). In spite of the added flexibility, the code size has shrunk from
> 3396 lines to 2912 lines. I plan to add support for binary data (e.g. ubyte -
> handling binary file formats can benefit a LOT from regexes) and also,
> probably unprecedented, support for arbitrary types such as integers,
> floating point
> numbers, structs, what have you. any type that supports comparison and ranges
> is a good candidate for regular expression matching. I'm not sure how regular
> expression matching can be harnessed e.g. over arrays of int, but I suspect
> some pretty cool applications are just around the corner. We can introduce
> that
> generalization without adding complexity and there is nothing in principle
> opposed to it.
>
> The interface is very simple, mainly consisting of the functions regex(),
> match(), and sub(), e.g.
>
> foreach (e; match("abracazoo", regex("a[b-e]", "g")))
> writeln(e.pre, e.hit, e.post);
> auto s = sub("abracazoo", regex("a([b-e])", "g"), "A$1");
BTW, why are the flags passed as string and not as an integer mask? For
example:
auto s = regex.sub("abracazoo", regex.regex("a([b-e])", regex.G), "A$1");
This way you can catch a few errors at compile-time.
--
Leandro Lucarella (luca) | Blog colectivo: http://www.mazziblog.com.ar/blog/
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