[Aldor-l] Should this "parser" work?

[Christian Aistleitner]

Hello Martin,

as you addressed the mail directly to me, I feel obliged to comment,  
although I cannot say anything new.

On Wed, 11 Oct 2006 11:43:01 +0200, Martin Rubey  
<martin.rubey at univie.ac.at> wrote:

> Consider the following snippet from Aldor-Combinat-experiments
>
> -------------------------------------------------------------------------------
>
> parse(s: String): ExpressionTree == {
> ...
> }
>
> -- evaluate basically replaces expressions "Self1", "Self2", etc.  
> appearing in
> -- t with the corresponding elements of selfList
> evaluate(
>     t: ExpressionTree,
>     selfList: List CombinatorialClass
> ): CombinatorialClass == {
> ...
> }
>
> grammar(p: List String): List CombinatorialClass == {
>         macro CC == CombinatorialClass;
>         import from MachineInteger, List CC;
>         A: CC == Atom;
>         res: List CC := [A for x in p];
>
>         E(i: MachineInteger): CC == evaluate(parse(p.i), res) add;
>
>         for i in 1..#p repeat res.i := E(i);
>         res;
> }
>
> -------------------------------------------------------------------------------
>
> Consider for example the effect of
>
> grammar(["Union(Atom, Cross(Self1, Self1))"])
>
> * res is initialized to [b] with "b" being an instance of the
>   CombinatorialClass Atom.

I am not to sure about whether or not “"b" being an instance of [...]  
Atom” is correct. As your situation is quite tricky, and you seem to look  
at the whole thing from a different angle than I am, can you explain to  
me, what happens internally, so that your code is working?

 From my point of view, your code looks like this in memory (I use the  
format
Adress: Data
. All references to other entities are explicitely written down). It  
translates

Definition of CombinatorialClass:
00001000: [...]

Definition of List( CombinatorialClass ):
00002000: [...] 00001000 [...]

Definition of Atom:
00003000: [...]

Definition of A:
00004000: [...] 00003000 [...]

Definition of res:
00005000:  00003000 00005010
00005010:  00003000 00000000

The grammar scope if the Universe (variable name, value, type) :
...
(A  , 00004000, 00001000 )
(res, 00005000, 00002000 )


into something I am not too sure about. Can you plot your ideas of what is  
going on in terms of such “virtual memory locations”. Especially the  
output of E(1) and its relation to res.


--
Kind regards,
Christian