Re: array conversion - how to do?

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <5p3rad$8n8$1@gonzo.sun3.iaf.nl> Geert Bosch <geert@gonzo.sun3.iaf.nl> writes:

  > The drawback of my generic Array_Conversion is that it is too powerful
  > in that it can convert an array of A to an array of B as long as B is
  > a new A. I would like to only allow conversion when A and B are subtype
  > compatible. Anyway, the point was to avoid copying as happens in the
  > loop approach, but at least GNAT doesn't seem to do that yet.

   One of those nasty "depend upon the compiler to do the right thing"
tricks you can use is to provide your own generic Checked_Conversion
routine which either does the run-time check OR just calls
Unchecked_Conversion if the source subrange is a subset of the target
subrange.  Even if the compiler is pretty dumb, you will at least get
a relatively quick check in the case where no check is required.  But
if the subranges are static and the compiler optimizes such generics
correctly (a pragma Inline can't hurt) the if statement will get
optimized away.

   A really fancy trick, and probably not worth the effort.  If the
ranges are nesting, you probably have more knowledge on the subject
than the compiler.



--

					Robert I. Eachus

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