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Glacial Grammar Engine -- a Perl 6 grammar engine written in Perl 6
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== Glacial Grammar Engine -- like PGE, but slower Ok, so there was some guy called Patrick who implemented a thing called PGE, right? It was this grammar engine written in PIR, the assembly language of Parrot. PGE was the first thing in the known universe that could parse Perl 6 regexes. It was then plugged into PCT, a toolkit for building HLL (Higher-Level Language) compilers for Parrot. Rakudo, a Perl 6 compiler, was then built on top of PCT. In short, a whole lot of abstractions, and in the bottom of it all, driving the parser, sits PGE. Humming along, it does all the daily parsing we now take, more or less, for granted. Patrick was once caught saying that given the little time he had spent optimizing PGE, he was surprised it wasn't actually much slower. What he might not have guessed was that this off-hand statement could be read as a challenge: PGE surprisingly not slow enough? We know a number of ways to fix that... GGE, the Glacial Grammar Engine, is a faithful port of PGE from PIR to Perl 6. It tries (albeit not too hard) to be implementation-independent, and it also attempts (though perhaps not too convincingly) to be a drop-in replacement for PGE. Most importantly, besides being written in Perl 6 rather than PIR, it brings one new essential feature to the table: it's slower. Much slower. Hence the name. The "albeit not too hard" reservation to the implementation-independence stems from the fact that some PIR tricks used by PGE are unavailable in Perl 6. When faced with a choice of (a) giving up, and (b) cheating by introducing some PIR-dependent workaround, the implementor of GGE will choose the latter road. That said, implementation-independence stands as a goal whenever possible, just as with all honest Perl 6 code. The "though perhaps not too convincingly" reservation to GGE attempting to be a drop-in replacement for PGE stems from the fact that now that regular expressions _are_ in fact available in the Perl 6 language (through PGE), it's sometimes too tempting not to use them. Of course, it would be a fun challenge in itself to restrict the writing of GGE to a strict subset of Perl 6 -- one not using any regexes at all, directly or indirectly -- but that is not the kind of fun optimized for in this case. Future teams of developers are welcome to optimize for that kind of fun, should they wish. == License Code coming from the Parrot repository is Artistic License 2.0. See LICENSE.