J3/11-214
To: J3
From: Malcolm Cohen
Subject: Multiple identical specific procedures in type-bound generic
Date: 2011 June 29

----------------------------------------------------------------------

NUMBER: F03/0018
TITLE: Multiple identical specific procedures in type-bound generic
KEYWORDS: Type-bound generic
DEFECT TYPE: Clarification
STATUS: J3 consideration in progress

QUESTION:

Q1. Does the following program unit conform to the Fortran standard?

  module M1
    type T
      integer x
    contains
      procedure :: MyAdd_t => myadd
      generic :: operator(+) => myAdd_t
    end type T
    type X
      real q
    contains
      procedure, pass(b) :: MyAdd_x => myadd
      generic :: operator(+) => myAdd_x
    end type X
  contains
    integer function MyAdd ( A, B )
      class(t), intent(in) :: A
      class(x), intent(in) :: B
      myadd = a%x + b%q
    end function MyAdd
  end module

Q2. Does the following program unit conform to the Fortran standard?

  module M2
    interface operator(+)
      procedure MyAdd
    end interface
    type T
      integer x
    contains
      procedure :: MyAdd_t => myadd
      generic :: operator(+) => myAdd_t
    end type T
  contains
    integer function MyAdd ( A, B )
      class(t), intent(in) :: A
      real, intent(in) :: B
      myadd = a%x + b
    end function MyAdd
  end module

Q3. If the interface block and type definition are exchanged in
    question 2, does the program unit conform to the Fortran standard?

ANSWER:

A1. The program unit is not standard-conforming.  Generic operator (+)
    has two ambiguous specific bindings, one to myadd_t the other to
    myadd_x.

A2. The program unit is not standard-conforming.  Generic operator (+)
    has two ambiguous specific procedures, one being the module
    procedure myadd the other being the type-bound procedure myadd_t.

A3. The ordering of the interface block and the type definition is
    immaterial.

EDIT:

None

SUBMITTED BY:  Van Snyder

HISTORY:  04-405    m170  F03/0018 submitted
          04-405r1  m170  Passed by J3 meeting
          05-146    m171  Passed J3 letter ballot #10
          N1658     m176  Failed WG5 ballot N1657
          11-nnn    m195  Revised answer.

----------------------------------------------------------------------