Prev: non printing characters
Next: Fortran problem
From: Uno on 6 Jul 2010 19:33
http://i48.tinypic.com/27wyvpg.png

I have read many times about fortran-c interop in c.l.f. and wanted to
search for these articles I have read. The screenshot shows how utter
this failure was.

q1) How do I do a keyword search of c.l.f.?
--
Uno
From: e p chandler on 6 Jul 2010 20:18
"Uno" wrote
> I have read many times about fortran-c interop in c.l.f. and wanted to
> search for these articles I have read. The screenshot shows how utter
> this failure was.

c interop real site:comp.lang.fortran
in the google search box comes up empty

> How do I do a keyword search of c.l.f.?

Try this instead
c interop real site:groups.google.com/group/comp.lang.fortran



From: Uno on 7 Jul 2010 00:29
e p chandler wrote:

> Try this instead
> c interop real site:groups.google.com/group/comp.lang.fortran

Alright, that does a lot better. (I entered that into my linuxlog.)

http://www.google.com/search?hl=en&as_q=+c+interop+real+site%3Agroups.google.com%2Fgroup%2Fcomp.lang.fortran+&as_epq=&as_oq=&as_eq=&num=10&lr=&as_filetype=&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images

So I poked around and didn't find exactly what I want there. I want a C
caller to print out the value of a fortran function that wraps an arctan
call:

$ gfortran -Wall -Wextra f_pi1.f90 -o out
$ ./out
3.1415927
$ cat f_pi1.f90
implicit none

! none of this yet
!integer, parameter, public :: sp = kind(1.0)
!integer, parameter, public :: dp = selected_real_kind(2*precision(1.0_sp))
!integer, parameter, public :: qp_preferred = &
!selected_real_kind(2*precision(1.0_dp))
!integer, parameter, public :: qp =
(1+sign(1,qp_preferred))/2*qp_preferred+ &
!(1-sign(1,qp_preferred))/2*dp

real :: constant, pi

constant = 4.0
pi = constant * atan(1.0)
print *, pi

end program
! gfortran -Wall -Wextra f_pi1.f90 -o out
$

A C program that does the same thing is:
$ gcc -std=c99 -Wall -Wextra c_pi1.c -o out
$ ./out
pi is 3.141593
$ cat c_pi1.c


#include <stdio.h>
#include <math.h>

// C will be caller

int main()
{

double d, pi;
d = atan(1.0);
pi = (4.0)*d;
printf("pi is %f\n", pi);

return 0;
}

// gcc -std=c99 -Wall -Wextra c_pi1.c -o out
$

q2) If this calculation is done in a posix-compliant environment, are
the widths of C's double and fortran's default real related?

Short of enlightment by google, I'm left to follow the development in
MR&C 14.10. The place where I lose my grip there is with the prototype

void simulation(struct pass *arrays);

that is called by

simulation(&arrays);

q3) Why does the MR&C development need the interface listed in figure
14.3 *and* the interface lsited in 14.4?

q4) If anyone has any suggestions regarding better search terms for
this question, I'm all ears.

Thanks for your comment, and cheers,
--
Uno

From: Tobias Burnus on 7 Jul 2010 02:07
First, I want to point out that there is some C interoperability
documentation at
http://gcc.gnu.org/onlinedocs/gfortran/Interoperability-with-C.html

Uno wrote:
> So I poked around and didn't find exactly what I want there. I want a C
> caller to print out the value of a fortran function that wraps an arctan
> call.

How about something like:

function myarctan(x) bind(C,name='myArctan')
use iso_c_binding
implicit none
read(c_double), VALUE, intent(in) :: x
real(c_double) :: myarctan
myarctan = atan(x)
end function myactan

and

double myArctan (double);
....
double x = ...
printf("myactan(%e) = %e\n", x, myArctan(x));


> q2) If this calculation is done in a posix-compliant environment, are
> the widths of C's double and fortran's default real related?

REAL(c_double) == double

etc. (using the intrinsic ISO_C_BINDING module of Fortran 2003, cf.
http://gcc.gnu.org/onlinedocs/gfortran/ISO_005fC_005fBINDING.html

Tobias
From: Uno on 7 Jul 2010 03:16
Tobias Burnus wrote:
> First, I want to point out that there is some C interoperability
> documentation at
> http://gcc.gnu.org/onlinedocs/gfortran/Interoperability-with-C.html
>
> Uno wrote:
>> So I poked around and didn't find exactly what I want there. I want a C
>> caller to print out the value of a fortran function that wraps an arctan
>> call.
>
> How about something like:
>
> function myarctan(x) bind(C,name='myArctan')
> use iso_c_binding
> implicit none
> read(c_double), VALUE, intent(in) :: x
> real(c_double) :: myarctan
> myarctan = atan(x)
> end function myactan

I've got a switch problem here, and looking at gcc.pdf and gfortran.pdf
in whatever crapass pdf viewer comes with ubuntu is availing me nothing.

I'm missing a switch here on the goocher, my commented-out command line:

$ cat f_pi2.f90
function myarctan(x) bind(C,name='myArctan')
use iso_c_binding
implicit none
read(c_double), VALUE, intent(in) :: x
real(c_double) :: myarctan
myarctan = atan(x)
end function myarctan

! gfortran -Wall -Wextra f_pi2.f90 -o fortranlib.o
$

How do I tell gfortran.exe not to expect main?
>
> and
>
> double myArctan (double);
> ...
> double x = ...
> printf("myactan(%e) = %e\n", x, myArctan(x));
>
>
>> q2) If this calculation is done in a posix-compliant environment, are
>> the widths of C's double and fortran's default real related?
>
> REAL(c_double) == double
>
> etc. (using the intrinsic ISO_C_BINDING module of Fortran 2003, cf.
> http://gcc.gnu.org/onlinedocs/gfortran/ISO_005fC_005fBINDING.html
>
> Tobias
 |  Next  |  Last
Pages: 1 2 3 4
Prev: non printing characters
Next: Fortran problem