Re: small example, using complex variables in Ada

[Stephen Leake <stephen_leake@stephe-leake.org>]

"Nasser M. Abbasi" <nma@12000.org> writes:

> I also wrote a FORTRAN equivalent of the small Ada function.  Here is
> below the Ada code, and the FORTRAN code.  Again, do not scream too
> much if it is not good code, I just learned this now, I am sure this
> can be improved a lot.

This is an interesting comparison. Perhaps, after people finish
polishing your code, you could publish it on
http://en.wikibooks.org/wiki/Ada_Programming 

> -- gnatmake dft.adb
> --
> -- ./dft.exe
> -- ( 6.00000E+00, 0.00000E+00)
> -- (-1.50000E+00, 8.66026E-01)
> -- (-1.50000E+00,-8.66025E-01)
> -- $
>
> ======= FORTRAN code ===========
> ! dtf.f90, compiled with GCC 4.3.4
> ! under CYGWIN 1.7.5
> ! gfortran -Wall dft.f90
> ! ./a.exe
> ! (  6.0000000    ,  0.0000000    )
> ! ( -1.4999999    , 0.86602557    )
> ! ( -1.5000005    ,-0.86602497    )
> !

It would be good to explain the small differences here; something about
how the floating point options are set, I suspect.

It would be good to state the theoretically correct answer; I hope it's
1.5, not 1.499... :).

> Conclusion:
> I actually liked the Ada implementation more than FORTRAN because:
>
> 1. In Ada, I did not have to change the index of m and k in the
> summation to reflect the 1-off per the definition of DFT.
> DFT starts from 0 to N-1. In Ada, using 'Range and defining the arrays
> to go from 0 .. N-1 solved the problem.
>
> 2. In Ada, the compiler complained more times more about types being
> mixed up. I placed float() around the places it complained about.

It's interesting that you list this as a bonus; some people would list
it is a negative feature ("_obviously_ the compiler should do that
conversion for you!").

> 3. It actually took me less time to do the Ada function than the
> FORTRAN one, even though I am equally not familiar with both at this
> time :)

That is my general experience with Ada; it takes less time to get the
result I want.

-- 
-- Stephe