[antlr-interest] Re: Please - can someone help me out?

[Geir Ove Skjaervik]

Hello,

and thanks for the clarifying answers! I see what you mean by 
unsolved references problem: I think I did a two pass in my hand 
coded parser: Thus, I will probably be better of Walking the Tree 
(line :-)). And as you say; I get the conext info for "free" which 
can be usefull for the debugger.

The next thing I would love to get my hands on, is this: An ANTLR 
example aka. the Calc example, but that also adds: function 
definition and function call AND walks a tree to execute the stuff. 
The problem with the provided examples like TinyBasic is that it is 
to big, to much to grasp. A very simple example makes it easier to 
grasp the principle and get flying. I am currently reading the ANTLR 
Reference Manual, but that is a time consuming feat....

Geir Ove


--- In antlr-interest at yahoogroups.com, "John D. Mitchell" <johnm-
antlr at n...> wrote:
> >>>>> "Geir" == Geir Ove Skjaervik <geiroves at o...> writes:
> [...]
> 
> > Q1: As for how to use ANTLR to implement a Stack Machine: 
Couldn't I
> > simply emit the stack instructions from the Parser part of ANTLR?
> > (That's what I did in the hand coded lexer / parser I wrote). 
What are
> > the benefits of doing it walking an AST tree?
> 
> Can you do a purely syntax-directed translation for your 
language?  E.g.,
> the answer is basically "no" if you have unresolved forward 
references that
> you have to fix up.  [Of course, you could have your stack machine
> evaluator be more complicated and do the fix-ups for you but that 
is, in
> essence, another pass so you've just moved the problem from one 
place to
> another.]
> 
> 
> > I feel pretty comfortable setting up the Lexer and Parser part 
in ANTLR
> > (I think), but the TreeParser part is unfamiliar ground although 
I think
> > I grasp the basics.
> 
> > Q2: What would be easier: Implementing a debugger for the Stack 
Machine
> > or the solution where code is executed walking the tree (is this 
called a
> > register machine?)
> 
> (A) They are basically equivalent given good engineering (i.e., 
good
> factoring).  The stack evaluator is a bit more localized but the 
tree
> evaluator has the explicit context of the tree.
> 
> (B) A register machine is something that looks like a CPU.  I.e., 
it's
> model wherein there are (banks of) registers in which computation 
takes
> place, usually some form of "hardware" supported stack, and 
general/heap
> memory.  GCC's RTL is an example of an intermediate representation 
(IR)
> of a register machine model.
> 
> Hope this helps,
> 		John





 
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