Re: What good are File_Access's?

[stt@houdini.camb.inmet.com (Tucker Taft)]

dennison@telepath.com wrote:

: It looks to me like the whole point of the File_Access type in Ada.Text_IO is
: to allow Standard_Output and Current_Output (and the same functions for Input
: and Error) to be compared in order to see if I/O has been redirected somehow.

Interesting...  The real reason was so that you could save the value of
"current_output", change it to something else, and then set it back.
I don't believe we ever discussed the idea of whether the equality operator
should return something meaningful for two different File_Access values
which in some sense designate the "same" file.

: However, when I compile and execute a DOS program using ObjectAda on NT,
: Ada.Text_IO.Current_Output and Ada.Text_IO.Standard_Output are *not* equal. If
: I do an Ada.Text_IO to either, it gets printed in my shell window.

: So if I can't use the equality operations of File_Access to see where output
: is going, what was the type put in there for? There's nothing else other than
: the Standard* and Current* functions that give me one, and the only
: operations allowed are equality comparison and assignment.

: T.E.D.

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--
-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
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