Re: small example, using complex variables in Ada

["Nasser M. Abbasi" <nma@12000.org>]

On 6/14/2010 2:33 AM, Vincent LAFAGE wrote:

> For instance,
>    $ gfortran-4.3 -Wall -Wsurprising -Wconversion dft.f90 -o dft
> will reveal 11 surprising implicit conversion such as
>    dft.f90:14.29:
>     COMPLEX, parameter :: J =(0,1)
>                                1
>    Warning: Conversion from INTEGER(4) to REAL(4) at (1)
>
> So "-Wall" is not the last word as far as warning are concerned.
>

Thanks, I did not know about these flags. I am impressed now with FORTRAN.

The f90 compiler, with those flags added, became as annoying, opps, I 
mean as picky as the Ada compiler and complained about all the implicit 
conversions.

Also, with the use of  lbound and ubound in FORTRAN helped make the 
logic simpler by avoiding the 1-off problem.

To update, below is the current version of the example in Ada and 
FORTRAN. I also made a small page where I kept these for reference.

http://12000.org/my_notes/mma_matlab_control/KERNEL/node94.htm

I think now it seems to me, from this simple example, that Ada and 
FORTRAN can be equally good languages for scientific applications.

Thanks for everyone for the suggestions.

============= Ada ====================
--
-- dtf.adb, compiled with GNAT 4.3.4 20090804 (release) 1
-- under CYGWIN 1.7.5
-- $ gnatmake dft.adb
-- gcc -c dft.adb
-- gnatbind -x dft.ali
-- gnatlink dft.ali
-- $ ./dft.exe
--
-- ( 6.00000E+00, 0.00000E+00)
-- (-1.50000E+00, 8.66026E-01)
-- (-1.50000E+00,-8.66025E-01)

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Numerics.Complex_Types; use  Ada.Numerics.Complex_Types;

with Ada.Numerics; use  Ada.Numerics;

with Ada.Numerics.Complex_Elementary_Functions;
use  Ada.Numerics.Complex_Elementary_Functions;

with Ada.Complex_Text_IO; use Ada.Complex_Text_IO;

procedure dft is
      N : constant := 3; -- named number, no conversion to Float needed
      X : array(0 .. N-1) of Complex  := (others=>(0.0,0.0));
      data : constant array(0 .. N-1) of float :=(1.0,2.0,3.0);
      Two_Pi_Over_N : constant := 2 * Pi / N;
       -- named number, outside the loop, like in ARM 3.3.2(9)
begin
      FOR k in X'range LOOP
          FOR m in data'range LOOP
              X(k) := X(k) + data(m)*exp(-J*Two_Pi_Over_N * float(m*k));
          END LOOP;
          put(X(k)); new_line;
      END LOOP;
end dft;

====================== Fortran ======================
! dtf.f90, compiled with GCC 4.3.4
! under CYGWIN 1.7.5
!  $ gfortran -Wall -Wsurprising -Wconversion dft.f90
!  $ ./a.exe
! (  6.0000000    ,  0.0000000    )
! ( -1.4999999    , 0.86602557    )
! ( -1.5000005    ,-0.86602497    )
!  $

PROGRAM dft

   IMPLICIT NONE

   INTEGER, parameter :: N = 3
   COMPLEX, parameter :: J =(0.0,1.0)
   REAL,    parameter :: Pi = ACOS(-1.0)
   INTEGER                   :: k,m
   COMPLEX, dimension(0:N-1) :: X
   REAL,    dimension(0:N-1) :: data=(/1.0,2.0,3.0/)
   REAL,    parameter        :: Two_Pi_Over_N = 2.0*Pi/real(N)

DO k = lbound(X, 1), ubound(X, 1)
    X(k)=(0.0,0.0)
    DO m = lbound(data, 1), ubound(data, 1)
       X(k) = X(k) + complex(data(m),0.0)                   &
              * EXP(-J*complex(Two_Pi_Over_N*real(m*k),0.0))
    END DO
    print *,X(k)
END DO

END PROGRAM dft


--Nasser