Re: Ada vs Fortran for scientific applications

["Jan Vorbrüggen" <jvorbrueggen@not-mediasec.de>]

> In contrast, f77 says, in its section on complex type (4.6)
> 
>   "The representation of a complex datum is in the form of an ordered
>    pair of real data. The first of the pair represents the real part
>    of the complex datum and the second represents the imaginary part.
>    Each part has the same degreee of approximation as for a real datum.
>    A complex datum has two consecutive numeric storage units in a
>    storage sequence: the first storage unit is the real part and the
>    second storage unit is the imaginary part."
> 
> While the wods about an ordered pair look pretty similar, the f77
> version has the word "representation", while the f2003 version doesn't.
> That makes them say different things acccording to me, although I'm sure
> the difference is unintentional. The f77 version seems to me to say the
> same thing twice, but the f2003 version dropped it down to zero  times.

It seems to me that F77 is saying two different things here: one is about
representation, and the second is about storage sequence and association.
They overlap in that the first statement includes the word "ordered", al-
though one could conceivably debate (in the Talmudic sense) whether that
should be understood with regard to storage sequence in the same way as
the second phrase nails things down.

Given the declaration

	COMPLEX X(10)
	REAL Y(20)
	EQUIVALENCE (X, Y)

I understand that at least F77, and by intent (your interpretation) later
Fortran standards force the compiler to have the piece of code

	X(3) = (4711., 0.815)
	PRINT *, Y(6)

result in an approximation of 0.815 being printed. This would indeed make a
different implementation more difficult.

	Jan