Re: what means the " ' " in use with a record type?

["Ben Brosgol" <brosgol@world.std.com>]

Tom Moran wrote:
>   I suspect that qualified expressions are fairly rare in practice
> except for an allocation with an initial value.
>
> >    x := new (value => x, to => 1);
> >
> > then the allocator has no idea what you are talking about, since there
is
> > nothing to say that this is a node. The qualified expression fixes this
>   If x is an access to type node, why is the qualified expression needed,
> while it's not needed in:
>   type fruits is (apple, orange, banana);
>   type colors is (red, orange, yellow);
>   color : colors;
>   fruit : fruits;
> begin
>   color := orange;
>   fruit := orange;

As I recall, the original reason for the apostrophe is because, in the
absence of this feature, the general construct
  new T(expr)
could be ambiguous (or at least confusing to the human reader) in some
contexts -- i.e., is expr the value of a discriminant, or is it an
initialization for the allocated object?  The apostrophe clearly indicates
the intent, and can also serve the purpose of a type qualification as Robert
observed.

Ben Brosgol
Ada Core Technologies