RETURN

RETURN [expr]

expr	Is a scalar expression that is converted to an integer value if necessary. The expr is only allowed in subroutines; it indicates an alternate return. (An alternate return is an obsolescent feature in Standard Fortran.)

説明

When a RETURN statement is executed in a function subprogram, control is transferred to the referencing statement in the calling program unit.

When a RETURN statement is executed in a subroutine subprogram, control is transferred to the first executable statement following the CALL statement that invoked the subroutine, or to the alternate return (if one is specified).

例

The following shows how alternate returns can be used in a subroutine:

   CALL CHECK(A, B, *10, *20, C)

   ...

10 ...

20 ...

   SUBROUTINE CHECK(X, Y, *, *, C)

   ...

50   IF (X) 60, 70, 80

60   RETURN

70   RETURN 1

80   RETURN 2

   END

The value of X determines the return, as follows:

• If X < 0, a normal return occurs and control is transferred to the first executable statement following CALL CHECK in the calling program.

• If X = = 0, the first alternate return (RETURN 1) occurs and control is transferred to the statement identified with label 10.

• If X > 0, the second alternate return (RETURN 2) occurs and control is transferred to the statement identified with label 20.

Note that an asterisk (*) specifies the alternate return. An ampersand (&) can also specify an alternate return in a CALL statement, but not in a subroutine's dummy argument list.

The following shows another example:

     SUBROUTINE Loop

     CHARACTER in

 10  READ (*, '(A)') in

     IF (in .EQ. 'Y') RETURN

     GOTO 10

 !   RETURN implied by the following statement:

     END

 !The following example shows alternate returns:

     CALL AltRet (i, *10, *20, *30)

     WRITE (*, *) 'normal return'

     GOTO 40

 10  WRITE (*, *) 'I = 10'

     GOTO 40

 20  WRITE (*, *) 'I = 20'

     GOTO 40

 30  WRITE (*, *) 'I = 30'

 40  CONTINUE

     END

     SUBROUTINE AltRet (i, *, *, *)

     IF (i .EQ. 10) RETURN 1

     IF (i .EQ. 20) RETURN 2

     IF (i .EQ. 30) RETURN 3

     END

In this example, RETURN 1 specifies the list's first alternate-return label, which is a symbol for the actual argument *10 in the CALL statement. RETURN 2 specifies the second alternate-return label, and RETURN 3 specifies the third alternate-return label.