steve@sdcrdcf.UUCP (Steven Holtsberg) (02/19/86)
I have read the paragraph on index constraints (page 3-29,
second from bottom) over and over, and I still do not know
what they are talking about.
It says:
If an index constraint follows a type mark in a subtype
indication, then the type or subtype denoted by the
type mark _must not already impose an index constraint_.
The type mark must denote either an unconstrained array
type or an access type whose designated type is such an
array type.
As I understand it, an index constraint (page 3-27) is a list of ranges
or subtype indications. So, if it follows a type mark, we have
something like:
INTEGER INTEGER range 0 .. 100
or
INTEGER range 0 .. 100
The first makes no sense, so I assume they mean the second, which
is an index constraint itself (as well as one that follows a type mark).
On the same page, there is an example,
type T is array(POSITIVE range MIN .. MAX) of COMPONENT;
It seems that the type mark in question is POSITIVE and
the index constraint is
range MIN .. MAX.
So, this means that POSITIVE must not already impose an index
constraint. But this makes no sense: although predefined
(see page 3-32), POSITIVE has the constraint 1 .. INTEGER'LAST.
The only thing I can infer is that the type of subtype denoted
by the type mark cannot impose a user-defined index constraint.
I am not sure of this- is there any agreement on the net?
However, the next sentence really confuses me:
The type mark must denote either an unconstrained array type
or an access type whose designated type is such an array type.
POSITIVE certainly does not satisfy this condition.
Does anyone know what they are talking about?