An interface block can be used to specify a generic name to reference all of the procedures within the interface block.
The initial line for such an interface block takes the following form:
This kind of interface block can be used to extend or redefine a generic intrinsic procedure.
The procedures that are given the generic name must be the same kind of subprogram: all must be functions, or all must be subroutines.
Any procedure reference involving a generic procedure name must be resolvable to one specific procedure; it must be unambiguous. For more information, see Unambiguous Generic Procedure References.
The following is an example of a procedure interface block defining a generic name:
INTERFACE GROUP_SUBS SUBROUTINE INTEGER_SUB (A, B) INTEGER, INTENT(INOUT) :: A, B END SUBROUTINE INTEGER_SUB SUBROUTINE REAL_SUB (A, B) REAL, INTENT(INOUT) :: A, B END SUBROUTINE REAL_SUB SUBROUTINE COMPLEX_SUB (A, B) COMPLEX, INTENT(INOUT) :: A, B END SUBROUTINE COMPLEX_SUB END INTERFACE
The three subroutines can be referenced by their individual specific names or by the group name GROUP_SUBS.
The following example shows a reference to INTEGER_SUB:
INTEGER V1, V2 CALL GROUP_SUBS (V1, V2)
Consider the following:
INTERFACE LINE_EQUATION SUBROUTINE REAL_LINE_EQ(X1,Y1,X2,Y2,M,B) REAL,INTENT(IN) :: X1,Y1,X2,Y2 REAL,INTENT(OUT) :: M,B END SUBROUTINE REAL_LINE_EQ SUBROUTINE INT_LINE_EQ(X1,Y1,X2,Y2,M,B) INTEGER,INTENT(IN) :: X1,Y1,X2,Y2 INTEGER,INTENT(OUT) :: M,B END SUBROUTINE INT_LINE_EQ END INTERFACE
In this example, LINE_EQUATION is the generic name which can be used for either REAL_LINE_EQ or INT_LINE_EQ. Fortran selects the appropriate subroutine according to the nature of the arguments passed to LINE_EQUATION. Even when a generic name exists, you can always invoke a procedure by its specific name. In the previous example, you can call REAL_LINE_EQ by its specific name (REAL_LINE_EQ), or its generic name LINE_EQUATION.
For More Information:
For details on interface blocks, see INTERFACE.