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From: belteshazzar <gbelteshazzar@gmail.com>
Newsgroups: comp.lang.ada
Subject: Unconstrained Arrays
Date: Mon, 16 Mar 2009 17:59:35 -0700 (PDT)
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Date: 2009-03-16T17:59:35-07:00
List-Id: <comp.lang.ada>

I have a program that uses a lot of different sized arrays and passed
into math functions. So I'm using an unconstrained array type. The
problem that I have is that I'm not allowed to use "new" this means
that I have to use pools (which I can't because to intantiate a pool I
have to constrain the array type) or allocated the arrays on the
stack. Allocating the arrays on the stack is fine, BUT it means that i
have to use array initializers so that they remain unconstrained
rather than becoming an anonomous contrained type that can no longer
be passed to my math functions.

We have now noticed that because of the size of our arrays that the
array intialisation is causing significant performance issues. Thus,
we need a new way of handling our arrays.

The best option seems to be to turn the functions that take arrays
into generic functions and instantiate them on the fly according to
the required size. Does anyone know if there are performance issues
with dynamically creating instantiations of generic functions all over
teh place?

Also, and the main point of my post, I've found that I can place the
unconstrained array inside a record with a distriminant and this seems
to solve all our problems. We don't have to use array initialisers and
we can get pointers to aliased objects that can be easily passed to
the math functions.

Has anyone come across these sorts of issues? I'm curious as to the
solution that others have found, and why Ada seems to handle
unconstrained arrays differently to unconstrained arrays inside a
record.