Re: Module variable name

[Richard E Maine <Richard dot Maine at nasa dot gov>]

On Oct 13, 2005, at 8:44 AM, Salvatore Filippone wrote:

> I had a Fortran module defining an explicit interface in which one of
> the dummy arguments had the same name as the module itself
...
> Question: is this specified by the standard?

Well, I'm a little unclear on exactly what you mean by "this". But 
anyway...

Module names are specifically *NOT* in any special separate category in 
the standard. A module name is just a global name and follows the same 
rules as any other global name (external procedure names, etc). There 
was once a proposal to make a separate class for module names, as they 
are always syntactically distinct (a USE statement being the only place 
they can appear other than the module/endmodule statements), but that 
propossal did not pass. It is an oversimplification to say that you 
can't have a module name be the same as the name of a dummy argument. 
There is not a rule like that. But there are rules that do apply. I 
would have to see the actual code - you haven't given enough 
information for me to be sure. I think your code might be ok, based on 
the description, but I'm not sure.

The short version is that you can't use the same name for 2 different 
purposes in the same scoping unit. There are exceptions, but none 
particularly relevant here. But your description doesn't make it clear 
whether or not you actually are using both names in the same scoping 
unit. I think maybe you aren't, but I can't tell for sure without 
seeing code. A case like

  module x
    interface
      subroutine sub(x)
      end subroutine sub
   end interface
end module x

is fine. That's because x is not used as a module name in the interface 
body. The normal host association rules apply; thus within the 
interface body, x is the dummy argument and cannot be used to refer to 
the module x.  But it is not used to refer to the module in the 
interface body, so all is fine. (Perhaps confusing, but 
standard-conforming).

But a case like

  module whatever
    interface
      subroutine sub(x)
        use x
     end subroutine sub
   end interface
end module whatever

is not standard-conforming because x is used for both purposes in the 
same scoping unit.

--
Richard Maine                |  Good judgment comes from experience;
Richard.Maine@nasa.gov       |  experience comes from bad judgment.
                            |        -- Mark Twain