(j3.2006) Interp 000068 and Fortran 2003

Michael Ingrassia michaeli
Tue Jan 2 17:02:12 EST 2007

Interp 000068 was one of the last interps processed for Fortran 95
that "would be in an F95 Corrigendum #3 if there were such
a corrigendum".

It says that the I/O unit identified by an asterisk for input or output
cannot correspond to more than one external unit.

On the face of it, that implies an implementation that takes advantage
of Fortran 2003's permission to use negative unit numbers for
INPUT_UNIT and OUTPUT_UNIT would have to give up using units 5 and 6
(respectively), because otherwise (say) stdin would be associated with
both unit 5 and a unit with negative unit number.

Somehow, it doesn't seem likely (to this vendor) that users would let us
stop using units 5 and 6 for stdin/stdout.  Doesn't this make negative
unit numbers completely unusable in practice ?

Assuming that negative unit numbers as permitted by the standard were
intended to be implemented, doesn't that mean that stdout (say) might
be identified with more than one external unit?  (Say, unit -3 and unit 6).
Do we need an interp to say so?

If so, should closing unit -3 affect unit 6 or vice versa ?
	--Michael I.

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