CONTAINS

Introduces an internal procedure or a module procedure.

Syntax

CONTAINS

Description

The CONTAINS statement introduces an internal procedure or a module procedure, separating it from the program unit that contains it. The statement can be used in:

When a CONTAINS statement is present, at least one subprogram must follow it.

Examples

The first example illustrates CONTAINS introducing an internal subroutine. It also illustrates how the internal subroutine mechanism can provide an alternative to the FORTRAN 77 statement function mechanism.

PRINT *, double_real(6.6)
CONTAINS
   FUNCTION double_real (x); REAL x
     double_real = 2.0 * x
   END FUNCTION
END

The next example illustrates a main program with an internal procedure part.

PROGRAM electric     ! Program header
   REAL  current     ! Specification part
   current = 100.5   ! Execution part begins
   CALL compute_resistance( voltage, current, resistance )
   CONTAINS          ! Internal procedure part
      SUBROUTINE  compute_resistance( v, i, r )
         REAL  i
         r = v / i
      END SUBROUTINE
END PROGRAM electric

The third example is of a module that contains a module subprogram, which in turn contains an internal subprogram.

MODULE one
   CONTAINS
   SUBROUTINE two(x)     ! Module subprogram
      CONTAINS
      LOGICAL FUNCTION three(y)   !Internal subprogram
      END FUNCTION three
   END SUBROUTINE two
END MODULE one

Related statements

SUBROUTINE and FUNCTION

Related concepts

For related information, see the following: