topic Re: Fortran problem in Operating System - OpenVMS

Fortran problem

Willem Grooters — Tue, 18 Dec 2007 19:47:46 GMT

See attachement (Fortan 8.2, Alpha)

The documentation is not clear about specifying STRUCTURE in an INTERFACE block.
What worries me most is that the strcucure isn't recognized at all. If I remove the Interface block or use INTEGER*4 and CHARACTER*(*), it's no problem at all.

What did I miss?

Re: Fortran problem

John Reagan — Tue, 18 Dec 2007 21:15:05 GMT

The manual clearly says: "An interface block comprises its own scoping unit, and does not inherit anything from its host though host association." That means that the structure X declared earlier is not visible inside the interface block. Things like INTERGER*4 or CHAR*(*) are builtin types that are available at any time.

Re: Fortran problem

Jess Goodman — Tue, 18 Dec 2007 23:20:05 GMT

You do need to define an explicit interface for function Y because it has an optional argument. However there are other ways to do this besides using an interface block.

You could just make function Y an internal procedure by defining it after a CONTAINS statement and moving the END PROGRAM to after END FUNCTION Y. You would then not need the INCLUDE statement inside the Y function definition.

Or you could define function Y in a MODULE. You would then add a "USE module_name" statement right after the PROGRAM X line.

For either of these alternatives remove the interface block from the include file.

Re: Fortran problem

Willem Grooters — Wed, 19 Dec 2007 06:36:14 GMT

John:
I must have overlooked that sentence, so that explaines why the strcuture isn't recognized in the INTERFACE block. I _think_ I found a way to get around it.

Jess:
This is just the reproducer, and in that context you are right, and I would have followed your suggestion anyway. In real, the problem occurs where the called routine ("Y" in the reproducer) is one of many in a library, called by many others. So your solution doesn't work here.

Re: Fortran problem

Willem Grooters — Wed, 19 Dec 2007 06:41:27 GMT

Jess:
Overlooked the second alternative :) That might work, if that allows "PRESENT" as a check whether an argument has been passed or not (IARGCOUNT may be sufficient in some cases and Ãs used where possible. But in some cases, this is not enough)

Re: Fortran problem

Willem Grooters — Thu, 20 Dec 2007 20:21:49 GMT

Could get around the problem - those routines that have a STRUCTURE typed argument have no optional arguments so can be kept outsize INTERFACE - for the sources at hand.