Re: [clisp-list] FFI improvements needed

[Hoehle, Joerg-C. <Joe...@t-...>]

Hi,

Bernard Urban wrote:
>> I don't understand what you mean. 2D arrays in CLISP (and 
>cmucl) are not pointer rows of pointers to doubles, (like 
>char*argv[]), they are n*m doubles in sequence.
>Yes, but in C, non-static 2D arrays are like char*argv[],
What's the definition of a non-static 2D array in C?

>and you are converting to such a beast.
No, I'm not! [cf. Monty Python]

>In Fortran, arrays are organized as in Lisp.
Row-major first, are your sure? Your code does it the other way round.

>> Otherwise, the following would yield garbage:
>> (with-c-var (m '(c-array uint8(2 3)) #2a((1 2 3)(4 5 6)))
>>   (cast m '(c-array uint8 6)))
>> -> #(1 2 3 4 5 6)
>Are you sure cast does not revert from the char*argv[] representtaion
>to the original ? My experiences with such things did not work in my
>lapack tests. 
FFI:CAST does nothing but check that SIZEOF and ALIGNOF match.

I'm sure I'm talking about 6 consecutive uint8 in memory. No *argv[].
There's a huge difference between
 (c-array (c-ptr (c-array x n) m) and
 (c-array (c-array x n) m).

I'm talking solely about the latter (2nd):
(with-c-var(m '(c-array uint8 (2 3)) #2a((1 2 3)(4 5 6)))
  (cast m '(c-array (c-array uint8 3) 2)))
-> #(#(1 2 3) #(4 5 6))
And it's an array of this kind that your initial cmucl and clisp code is filling.

(with-c-var(m '(c-array uint8 (2 3)) #2a((1 2 3)(4 5 6)))
  (cast m '(c-array (c-array uint8 2) 3)))
-> #(#(1 2) #(3 4) #(5 6))

>By the way, this is a method to coerce the rank of matrices !
It's exactly like the CLHS example on ARRAY-ROW-MAJOR-INDEX, showing off a displaced array using a different rank (giving a linear view on a matrix).

Regards,
	Jorg Hohle