null range from 1 element discrete type

[Duncan Sands <sands@topo.math.u-psud.fr>]

Suppose I have a discrete type (eg an enumeration type) T
containing just one element.  I would like to define a subtype
with a null range.  If T had more than one element, I could use
T'Last .. T'First, but this won't work here.  How to get a null
range in this case?

As you may guess, I have a generic package that takes a discrete
type parameter T, and I want it to work correctly in this degenerate
case.  At some point the package declares an array type, eg
type A is array (T range <>) of Float;
and I want to declare a null slice of type A.  At this point
I run into the above problem...

Thanks for any help,

Duncan.

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 Laboratoire de Topologie et Dynamique, Batiment 425,
 Universite de Paris-Sud, 91405 Orsay, France
 sands@topo.math.u-psud.fr
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