D grammar as LL(1) grammar ( OT)

[BCS]

Reply to Jascha,


> Furthermore, LR parsers consider multiple potential parse trees at the
> same time, throwing away the wrong guesses, once the necessary tokens
> get available. LL parsers have to check each potential parse tree
> separately.
> 

In general that may be true (I'd have to check) but often a specific grammar 
can be rearranges to (partly) avoid that, particularly the parts that appear 
in several trees.

for instance:

A ::= B c C | B d D | B e E ;

can be rearranged as

A ::= B A_ ;
A_ ::= c C | d D | e E ;

This at a minimum can avoid reparsing the B part of each option.

Admittedly this is actually changing the grammar that is being parsed (so 
I can't claim to be doing a better job with the original grammar) but these 
can be done automatically.