World: r3wp

btw, in your spec I noted that you have the comma identified as part 
of the syntax, that's invalid in REBOL.

You need to look at it as if you were building a dialect for REBOL 
that compiles to native code, but trying to keep the syntax and semantics 
as clean and familiar (from the REBOL user POV) as possible (trying 
to avoid C pitfalls while retaining its possibilities).

Comma: probably an error.

though it would be a welcome separator (ignored like a whitespace).

would make a lot of data readable by rebol directly which cannot 
be currently used.

The C-like way is to manage structs as structs. The reference limitation 
is only for function parameters and return types. Other languages 
(which also have libraries that we might want to access) support 
passing structs as parameters, and for internal use we definitely 
want to support in-memory structs.


Still, we have objects for in-memory structures, so we're good there. 
If you want to see a structure as a reference type, it could just 
be a metaphor for binary conversions. In that case, dropping the 
pointer type and just using struct! for that would work pretty well, 
and make dereferencing the pointer a simple matter of syntax, rather 
than a operator or built-in function.

Commas are valid in REBOL. They're used as decimal points, European-style.

And a leading comma is like + or - or . as a number prefix.

Max: that would be an issue as in french, for example, you write 
decimals with a comma. Also, I thinks it's too valuable to use in 
some literals to make it transparent for some rare use-cases.

well, use of comma as an alternative for decimals is a waste of a 
character.   commas have given me headaches in many apps where I 
had to build a string parser from scratch instead of just loading 
the string.

anyhow...  didn't know it was usable for decimals in REBOL .

>> 1,2
== 1.2

I have made a much more thorough set of parse rules for words in 
R3, including replicating the exact behavior of errors triggerd (except 
the Near field). See http://issue.cc/r3/1302for details.

Max: if you need to make commas LOAD-transparent in a string!, it 
is as easy as: replace/all string "," " "

It still doesn't handle the full set of Unicode, just ASCII, but 
I can reverse the charsets to be complemented opposites and it will 
handle those too.

C's struct! type is a roundabout way of specifying memory layout. 
A more direct way for specifying memory layout would certainly be 
nice, but if you want to interface with C-like code a lot, you'll 
want memory layout (storage) specifiers that allow you to mimic C 
(ABI) semantics.

Brian: I've bookmarked that ticket already. Will use your rules for 
defining Red's lexical analyzer.

I.e. while you can get rid of pointer! and just use &[integer!], 
that is fine. But if you specify integer! as always being a 32-bit 
integer, you lose out in hiding cross-platform quirks.

I'm hoing to expand them to be a full R3 code version of TRANSCODE, 
in a module.

You could just say that all references are structs, and that the 
pointer! type is a shortcut for making a struct! with a single field 
named value.

Andreas: that's the idea. All Red/System features are here to serve 
either the interfacing with OS and third-party libs (mostly C libs) 
or to serve the upper layer (Red) needs.

Though I would change this:
    p: &[pointer! [string!] 0]             ;-- char **p = 0
to this:
    p: &[&[string!] 0]                         ;-- char **p = 0

You can get rid of the pointer! name altogether and still keep the 
syntactic shortcut.

Then I'd keep the pointer! type as a specifier for the target platforms 
"pointer type".

Or you could call it handle! like R3 does.

The pointer! default value could always be 0 ,so that value could 
be removed from literals.

Then, real structure variables could be specified with #[struct! 
...] instead of reference types that are specified as & [ ].

#[struct! ...] can't work if I use non-REBOL datatype names...That's 
why I used 'struct as keyword to workaround that.

But you might be able to get by with only structure references and 
not have real structure variables. Then structs would be conversion 
metaphors.

The main advantage to real struct! variables rather than just reference 
types is bounds checking. Can you build in bounds checking into your 
reference use, or are you just hoping for the best? Since C doesn't 
have encoded bounds, struct! references used for C interop would 
have to follo the hope-for-the-best model.

Andreas, the target platform's pointer type points to something. 
Unless you know at least the size of that something, let alone its 
type, it is unsafe to use such a pointer. It is best to pretend that 
an untyped pointer is not a pointer at all, just a pointer-sized 
opaque value like R3's handle!. You can then explicitly convert that 
value to a typed reference in order to be able to use it as a pointer.

That is all fine and well, but won't help you interfacing with C 
code.

(Or other system ABI-compliant code, for that matter.)

Brian: I can't see how I could make Red/System safe while been able 
to fully interface with C code?

Or in other words: "pointer-sized opaque value" -- that's exactly 
what I'd use the pointer! type for.

With the focus on pointer-sized, not on opaque. The opaqueness is 
a separate issue, but you _need_ a specifier for pointer-sized values.

Sure it will, Andreas. The explicit conversion is just there to catch 
bugs in your code. The handle! type is just to interface C code that 
takes a void pointer. All other pointers would be struct! references. 
And this code:
    &[integer! 0]
would just be a syntactic sugar shourcut for this:
    &[struct! [value [integer!]] #{00000000}]
or something like that.

And then all C int* values would just correspond to that type.

Brian: is there any documentation about R3's handle! type? This page 
is empty: http://www.rebol.com/r3/docs/datatypes/handle.html

It's a value you can do nothing with :)

btw, when allocating arrays, the use of /value should not be required. 
 just like in C and REBOL's use of path notation, it should adapt 
to what is being pathed. 

using: 
p: &[array! [20 integer!] 0]

should be used with 
p/4: 123 

in fact:

 p/4/value: 123 

would be used for:
p: &[array! [20  &[integer!]] 0]

So the opaque pointer-to-? type would be called handle! for compatibility, 
and typed pointers would be handled by struct! references. And you 
can do inline struct! values like this:
    #[struct! [value [integer!]] [0]]

which is the serialized syntax for a struct! in R2, on R2 platforms 
that support structs.

Doc, if you match the serialized syntax for R2 structs then R2 can 
load your values to compile them.

Then you can have real structs as well as struct references.

Brian: that is what I was doing until I introduced the pointer! datatype. 
R2 chokes on pointer! in struct! specs.

Same goes for int8!, uint8!, ...

I think R2 will also choke on handle!.

(Didn't try, though.)

Right, same issue.

Yup. You would be limited in what types of structs you could declare 
as inline values in Red until you switch to your own loader. But 
you wouldn't be limited in what you can declare as struct! references.

AFAIK R2's struct!  can't properly represent many of the structs 
I've wanted to play around with.