Konstantin L. Metlov wrote:
> What I'm missing is the possibility to pass a pointer to the integrand
> function (written in J) into the Fortran or C code (called from J).
>
> I've seen the lab on callbacks, but they are only allowed to return a scalar
> integer result, while I'd like to be able to receive and pass back to Fortran
> (or C) a vector (of floats) or, even better, a general array. Is there
> another
> interface for writing external (defined in DLLs) adverbs (or conjunctions),
> taking a function (verb) as an argument ?
I'm completely ignorant in your problem domain, but it might use integer
argument to pass an address of any J noun using this verb.
iad=: 3 : 0
y=. y.
SZI=. IF64{4 8
ple=. 15!:6 <y
pa=. memr ple, SZI, 1, JPTR
''$pa+memr pa, 0, 1, JPTR
)
for example, p will be a pointer to memory block of content of array a.
a=: %: i. 3 4
p=. iad 'a'
memr p, 0 12 8
0 1 1.41421356 1.73205081 2 2.23606798 2.44948974 2.64575131 2.82842712 3
3.16227766 3.31662479
,a
0 1 1.41421356 1.73205081 2 2.23606798 2.44948974 2.64575131 2.82842712 3
3.16227766 3.31662479
In this manner it is possible to pass general array to C/Fortran, of course
C/Fortran has more work to do in order to decode a boxed array.
To pass array in the other direction C/Fortran -> J, to just pass the pointer to
the array and use memr in J to read its content.
--
regards,
bill
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