Re: Ada vs Fortran for scientific applications

[<adaworks@sbcglobal.net>]

"Gordon Sande" <g.sande@worldnet.att.net> wrote in message 
news:2006052509454116807-gsande@worldnetattnet...
>
> How many Ada systems can match the undefined variable checking of the
> old WatFor or the current Salford CheckMate or the Lahey/Fujitsu
> global checking? It seems to be a thing associated with places that
> run student cafteria computing on mainframes. Not much used anymore.
> There was a similar student checkout PL/I from Cornell if I recall
> correctly.
>
The default for Ada is to do thorough range checking on all numeric
types.   A designer may suppress that default, selectively, if it is deemed
unnecessary.

Ada allows the explicity declaration of range constraints, bit mapping,
and other low-level features.

Examples:

  type My_Number is range 3..56;    -- sets the upper and lower bounds
                                                        -- on an integer type

  type My_Float is digits 7 range -200.0 .. 500.0;
                                                       -- sets the number of 
digits
                                                       -- and the range for this 
type

These are just two examples.  The same thing can be done for decimal
types, modular types, fixed-point types, etc.

Ada also uses the name-equivalence, rather than the structural equivalence
approach to checking (at compile time).   Therefore,

       type N1 is range 0..100;
       type N2 is range 0..100;

with

       X : N1;   -- X is of type N1
       Y : N2;   -- Y is of type N2;

will reject,

       X := Y +1;   Y is incompatible, by name, with X;

Some languages will accept the above statement because the two
values have types that are structurally equivalent.

One of the principle features of Ada is the rigor of its checking both
at compile-time and run-time.  This includes indices, ordinary numeric
types, subscripts, etc.

Richard Riehle