Dear Marc,

Here is something that is really key for some lowlevel things: I wish to do the equivalent of the C expression * ((byte*) x) in the Scheme world, i.e. the same as something like MOV AL,[EAX] .

So, something like the C variant:

for (int i = 12345; i < 12445; i++)

print("%i ",* ((byte*) i));

would, if we call the read operator ##sysmem-byteref , be expressed in Scheme as something like:

(let loop ((i 12345))
(if (< i 12445)

(begin
(print (##sysmem-byteref i) " ")
(loop (##fxnum+ i 1)))))

We can call the write operator ##sysmem-byte-set! . Also it would be of great benefit to have one for 16bit, one for 32bit, one for 48bit and one for 64bit words.

I think it's justified that there is some way to reach this with highest efficiency, i.e. a way that does this inlined in the code thus producing something like * ((byte*) x) / MOV AL,[EAX] .

Indeed this would provide of good efficiency on 64bit machines only, where fixnums can go up to ~10^18 (unlike 32bit machines where it's ~0.5 * 10^9, so pointers would generally be bignums).

Is this in place already, if not how is it best implemented? (with ##c-code and some magick around it perhaps; I'd suppose with ##c-lambda there's always some handling around that would make it clearly more than a single-cpu-instruction operation, even if compiled with (declare (not safe)) ).

I may not be correct about this one but I got the impression that ##u8vector-ref/set! would *not* work for this, though perhaps a u8vector object could be produced that is immovable and has zero as its offset memory address?

Thanks,

Mikael