On Mon, Nov 21, 2005 at 02:05:31PM -0500, Rob Kinyon wrote:
: This is very close to a proposal I made to the ruby-dev mailing list
: (which was Warnocked). I proposed a very basic engine that would work
: with the parser/lexer to determine what action to take instead of
: using the huge case statements that are the heart of both P5 and Ruby.
: It would look something like:
:
: TOKEN:
: while ( my $token = get_next_token(<params>) ) {
: for my $length ( reverse length($token) .. 1 ) {
: if ( my $actions = find_actions( substr( $token, 0, $length ) ) ) {
: $action->[-1]->( < params, if necessary > );
: }
: next TOKEN;
: }
: throw SyntaxError;
: }
:
: The for-loop + substr() would be to handle longest-token-first rules.
: So, "..." is correctly recognized instead of handled as ".." and ".".
: The key would be that the $actions arrayref would get push'ed/pop'ed
: as you enter/leave a given lexical scope.
:
: Obviously, this could be optimized to an extremely large degree, but
: it -should- work.
Let's see, where did I put my stash of generic quotes? Ah, there is is.
"Those who do not understand XXX are doomed to reinvent it, poorly."
~~ s/XXX/the Perl 6 grammar engine/;
In particular, you've just reinvented the magic hash semantics mandated
by P6 rules, except that P6 has some hope of optimizing the lookups
to a cached trie or whatever.
Larry
