Let's stop parser Hell

[Roman D. Boiko]

On Saturday, 7 July 2012 at 22:45:01 UTC, Chad J wrote:
> I see what you mean.
And I think that I expressed myself badly. Let me rephrase.

When the memory hierarchy is deep, every level would require at 
least one bit position. Or even every base class would require a 
separate bit. (I think that the former + several bits to 
distinguish among hierarchies.) Otherwise it would not be easy to 
check by a bit-mask. Even if the above is incorrect (and that is 
likely since I didn't try to encode that compactly for the real 
grammar), I think that in general that information would only be 
possible to store in a fairly large integral. Especially if we 
try to generate parser from grammar, and thus can't do 
fine-tuning to pack the information tightly. This overhead would 
be paid per each AST node __instance__. But that is not 
necessary, since we could store information in a lookup table 
only once per node __type__.