alextsao1999 added inline comments.
================ Comment at: clang/include/clang/Tooling/Syntax/Pseudo/LRGraph.h:96 + uint8_t DotPos = 0; + uint8_t RuleLength = 0; // the length of rule body. +}; ---------------- sammccall wrote: > alextsao1999 wrote: > > hokein wrote: > > > alextsao1999 wrote: > > > > Can we add LookaheadSymbol here to implement LR(1)? > > > we could do that. However, we don't have a plan to implement an `LR(1)` > > > yet, we use `SLR(1)`. (though LR(1) is more powerful than SLR(1), the > > > typical deterministic LR(1) parser cannot handle the C++ grammar, we need > > > a "general" parser GLR which can be able to handle arbitrary context-free > > > grammars). > > Thanks for your answering! Oh, I know some `GLR` parsers are based on > > `LR(1)` or `LALR`, so I think our `GLR` parser is based on `LR(1)` as well. > > I'm trying to keep up with your train of thought :) > Yeah, GLR changes the tradeoff between more sophisticated and simpler parsers > (LR(1) > LALR > SLR(1) > LR(0)). > > Normally the sophisticated parsers are able to handle grammars/languages that > the simple ones can't, by avoiding action conflicts. So the value is very > high. > > However with GLR we can handle action conflicts by branching, so the value is > "only" avoiding the performance hit of chasing branches that don't go > anywhere. > > So it didn't really seem worth the extra implementation complexity (or extra > size of the in-memory grammar tables!) to use a more powerful parser than > SLR(1). Maybe we should even have given LR(0) more thought :-) Yes, agree. `SLR` can reduce memory usage, but it can't handle operator precedence. With the help of GLR, we can resolve the problem of operator precedence by chosing one branch. Thanks, I got it! Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D119172/new/ https://reviews.llvm.org/D119172 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
