On 2010-06-18 06:44, Andrei Alexandrescu wrote:
There are currently two regexen in the standard library. The older one, std.regexp, is time-tested but only works with UTF8 and has a clunkier API. The newer one, std.regex, is newer and isolates the engine from the matches (and therefore can reuse and cache engines easier), and supports all character widths. But it's less tested and doesn't have that great of an interface because it pretty much inherits the existing one.I wish to improve regex handling in Phobos. The most important improvement is not in the interface - it's in the engine. The current engine is adequate but nothing to write home about, and for simple regexen is markedly slower than equivalent hand-written code (e.g. matching whitespace). One great opportunity would be for D to leverage its uncanny compile-time evaluation abilities and offer a regex that parses the pattern during compilation: foreach (s; splitter(line, sregex!",[ \t\r]*")) { ... } Such a static regex could be simpler than a full-blown regex with captures and backreferences etc., but it would have guaranteed performance (e.g. it would be an automaton instead of a backtracking engine) and would be darn fast because it would generate custom code for each regex pattern. See related work: http://google-opensource.blogspot.com/2010/03/re2-principled-approach-to-regular.html If we get as far as implementing what RE2 can do with compile-time evaluation, people will definitely notice. If there's anyone who'd want to tackle such a project (for Phobos or not), I highly encourage you to do so. Andrei
The is already a compile time regular expression engine available in the DDL project at dsource, it's in the meta package: http://dsource.org/projects/ddl/browser/trunk/meta I don't know if it's is still usable.
-- /Jacob Carlborg
