Re: In-Out Parameters for functions

[Stuart Palin <stuart.palin@0.0>]

Hyman Rosen wrote:

> There are plenty of times where I am convinced that a position I hold
> has compelling counter-arguments. This is not one of them. I have yet
> to hear why a deliberate ambiguity is better than a definite order.

I am no expert in these matters, but I thought that at some
time in the [distant] past the argument was made that the
ambiguity allows optimization: in particular optimization in
systems employing highly parallel computing architectures.

In such systems, different parts of an expression could be
'farmed out' and computed in parallel because there was no
assumption of any sequential order.

This argument should also have merit in cases where
processors have multiple execution units and support for
out-of-order execution.  Just how far must a compiler go in
preserving the sequential order written in the source code?

I would agree with you that in most run-of-the-mill software
cases the lack of definite execution order does create a
pitfall for the unwary.  But, it also creates an opportunity
for 'smart compilers' to optimize.  In the end, surely, the
language must strike a balance in judging the true intent of
an author (when they are writing vanilla programs).  Is the
serialization of an expression a specific requirement or an
unwanted by-product of the format of the source code!

On balance [however much I might find it a pain in my line
of programming], I think that the language has chosen the
most pragmatic approach.  Those of us who are really
concerned about the matter will add it to our list of
concerns [and then probably turn to SPARK to save us from
ourselves :-) ]

--
Stuart Palin