Re: Ada vs Fortran for scientific applications

["James Giles" <jamesgiles@worldnet.att.net>]

adaworks@sbcglobal.net wrote:
...
> [...]         However, since the compiler will emit a warning
> about variables that have never been assigned a value in an algorithm
> that tries to use it, no harm is really done since the careful
> programmer will not release a program with warnings in it.

It's not always possible to detect that at compile time.
The execution of the code may depend on input data.
I'm guessing that your implementation emits a warning
if it detects that a *possible* control path includes a
use without a previous definition (that's presumably
why it's a warning and not fatal).

Nor is initialization a very good solution.  Well, unless
you have a value you can initialize with that's obviously
wrong (that's why IEEE has NANs).  Initializing with
an arbitrary plausible value often conceals errors and
leads to plausible wrong answers.  I still remember many
cases where people developed a code in an implementation
that always set all of memory to zero, but subsequently
move to an implementation that did not.  When their code
crashed they wanted to know how to get their new
implementation to clear all of memory so they could
get their old "correct" answers.  I've seldom seen cases
of this where the old answers were really correct.

Runtime testing can be expensive.  But there are cases
where it's the only reliable way.

-- 
J. Giles

"I conclude that there are two ways of constructing a software
design: One way is to make it so simple that there are obviously
no deficiencies and the other way is to make it so complicated
that there are no obvious deficiencies."   --  C. A. R. Hoare