Hacker News new | ask | show | jobs
by chrisseaton 1759 days ago
> That depends on the language you're trying to parse.

Yes... but most practical languages do not have simple LL or LR grammars. Hence this blog post and discussion and these problems.
1 comments
Zababa 1759 days ago
That's not true. You can have a LL or LR grammar, and use a hand-written parser to get better speed, better error reporting, any number of reasons really. Java is LL(1), but javac seem to use a hand-written recursive descent parser. Now that I think about it, Java being omitted is weird.
link
UncleEntity 1759 days ago
> Java is LL(1)...

Java hasn't ever been able to be parsed with one token look ahead, the earlier versions had a section on how to modify the grammar to be LALR(1)[0] but it was dropped in later versions of the specification -- probably due to added features which made it unfeasible like generic classes.

It's actually quite a good resource since they explain the reasons why the parser needs to have more than one token to figure out what's going on.

[0] http://titanium.cs.berkeley.edu/doc/java-langspec-1.0/19.doc...

link
chrisseaton 1759 days ago
What’s not true?

I said ‘most’ not ‘all’, and nobody here said the only reason to hand-write a parser was context sensitivity.

link