[antlr-interest] Re: Nondeterminism problem

[Oliver Zeigermann]

sarah2geller wrote:

> --- In antlr-interest at yahoogroups.com, Terence Parr <parrt at c...> 
> wrote:
> 
>>On Friday, December 19, 2003, at 12:09 PM, sarah2geller wrote:
>>
>>>Since t is not on the right side of a production, the t 
> 
> production is
> 
>>>not reachable in the grammar.
>>>
>>>As I said before, LL(1), SLL(1), and LALL(1) are all the same 
> 
> grammar
> 
>>>class. This is a well-known fact that you can find in any text 
> 
> book.
> 
>>I think you'll find it says more precisely that LL(1) can be 
> 
> rewritten 
> 
>>as SLL(1) but they are not the same class of grammars.  Same class 
> 
> of 
> 
>>languages, though. :)
>>
> 
> 
> No, I won't find this at all. Give a reference instead of hot air.
>  

Hmmm, the misunderstanding seems to be based on the difference between 
SLL (=simply LL) and strong-LL. As indicated by the reference Sarah 
already gave:

http://www.cs.vu.nl/~dick/PTAPG.html

p. 174, 8.2.3 claims every strong-LL(1) is LL(1) and the other way 
round, but not true for k > 1. This is what Sarah says. Now on p.167, 
8.1 it says *simple LL(1)* also called *SLL(1)* is a subset of LL(1) 
which is obvious when we have a look at the informal definition: "all 
right-hand sides of a non-terminal start with a different terminal 
symbol". That's what Terence said. Both are more or less right then, but 
were just using those confusing names differently.

So, folks, calm down :)

Oliver



 

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