Duplicate Arguments

The same actual argument cannot be used more than once in a procedure call if the corresponding dummy arguments are assigned new values. For example, with:

 
       SUBROUTINE FUNNY(X, Y) 
       X = 2.0 
       Y = 3.0 
       END

A call such as:
CALL FUNNY(A, A)
would be illegal because the system would try to assign both 2.0 and 3.0 to the variable A.

A similar restriction applies to variables which are returned via a common block and also through the procedure argument list.