Re: Enumeration_IO

[Robert Dewar <robert_dewar@my-deja.com>]

In article <38ED2AC4.A7B9147B@acm.org>,
  jrcarter@acm.org wrote:

> Enumeration_IO is in Ada.Text_IO;

Yes, that's right

> look for a-textio.ad?

But that interestingly is wrong, internally GNAT handles
Enumeration_IO as a child unit. This has the advantage that
it is only loaded if needed.

Of course if Ada 95 had been designed from scratch then of
course Enumeration_IO would be a child unit, but we had to
be compatible with Ada 83, so we could not do this.

GNAT has some interesting internal circuits to implement
these subpackages of Text_IO as child packages, while preserving
the unfortunate subpackage semantics of the Ada 83 (and hence
Ada 95) definitions.

So the file to look in for this stuff is

a-tienio.ad? (Ada.Text_IO.Enumeration_IO)

Examine the compiler sources for more information on the
internal handling of this interesting transformation.


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