procedure argument

a question regarding the usage of procedure arguments with different
argument lists.

the appended code compiles and writes out:

sub1: a= 1.0
sub2: a= 1.0 , b= 2.0

when i replace the two "EXTERNAL sub" statements by interface blocks

INTERFACE
SUBROUTINE sub (a,b)
REAL :: a,b
END SUBROUTINE sub
END INTERFACE

the compiler complains (as it should) about the different number of arguments of actual and dummy procedure.

why does it accept the EXTERNAL statements?

thanks,
roland


MODULE testmod
INTERFACE
SUBROUTINE sub1 (a)
REAL :: a
END SUBROUTINE sub1
END INTERFACE
INTERFACE
SUBROUTINE sub2 (a,b)
REAL :: a,b
END SUBROUTINE sub2
END INTERFACE
INTERFACE
SUBROUTINE process (sub)
EXTERNAL sub
REAL :: c=1.0,d=2.0
END SUBROUTINE process
END INTERFACE
END MODULE testmod

PROGRAM testprog
USE testmod, ONLY: sub1,sub2,process
CALL process (sub1)
CALL process (sub2)
END PROGRAM testprog

SUBROUTINE process (sub)
EXTERNAL sub
REAL :: c=1.0,d=2.0
CALL sub (c,d)
END SUBROUTINE process

SUBROUTINE sub1 (a)
REAL :: a
WRITE(*,*)'sub1: a= ',a
END SUBROUTINE sub1

SUBROUTINE sub2 (a,b)
REAL :: a,b
WRITE(*,*)'sub2: a= ',a,', b= ',b
END SUBROUTINE sub2
.

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