Fortran operator overloading with generic function

Question

I would like to use the generic name of a function to overload the '*' operator as in the example below:

interface scala
    module procedure :: scalapr,scalarp
end interface scala
interface operator(*)
   module procedure :: scala
end interface operator(*)

However, compiling with gfortran, I get:

Error: Procedure 'scala' in intrinsic '*' operator at (1) is neither function nor subroutine

Is there any turn-around ?

Vladimir F Героям слава · Accepted Answer · 2017-05-25 10:56:38Z

2

You must overload with the specific function

interface scala
    module procedure :: scalapr,scalarp
end interface scala
interface operator(*)
   module procedure :: scalapr, scalarp
end interface operator(*)

The generic is not a module procedure, so it cannot appear in module procedure.

There is also just procedure, but that won't help here. It is for procedures not coming form the current module. But anyway, the functions in the generic interface block must be specific functions.

See Fortran 2008 12.4.3.4 Generic interfaces:

1 A generic interface block specifies a generic interface for each of the procedures in the interface block. The PROCEDURE statement lists procedure pointers, external procedures, dummy procedures, or module procedures that have this generic interface. ...

According to 7.1.6:

5 A function defines the binary operation x1 op x2 if
  (2) either
     (a)  a generic interface (12.4.3.2) provides the function with a generic-spec of OPERATOR (op),
  or
     (b)  there is a generic binding (4.5.5) in the declared type

so the rules above do apply as does the constraint

C1207 (R1206) A procedure-name shall be a nonintrinsic procedure that has an explicit interface.

A generic-name does not conform to C1207.

edited May 25, 2017 at 10:56

answered May 25, 2017 at 5:55

Vladimir F Героям слава

60.7k4 gold badges82 silver badges131 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

GiorgioP-DoomsdayClockIsAt-89 Over a year ago

That was clear from the compiler message. My question was if there is any alternative.

Vladimir F Героям слава Over a year ago

Nope, there isn't. That's what I am saying. (You would be surprised how many people here don't read or don't try to understand compiler messages.)

Collectives™ on Stack Overflow

Fortran operator overloading with generic function

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related