Open Watcom FORTRAN 77 Language Reference

Functions and Subroutines
Example:
SUBROUTINE CALC( U, V )
REAL POLY, X, Y, U, V, Z, CONST
*
* Define a Statement Function.
*
POLY(X,Y) = X**2 + Y**2 + 2.0*X*Y + CONST
*
* Invoke the Statement Function.
*
CONST = 23.5
Z = POLY( U, V )
PRINT *, Z
END
In the previous example, note that after the execution of the statement function, the values of X and Y are
not equal to the value of U and V respectively; they are undefined.
12.2.2 Statement Function Restrictions
1. A statement function is local to the program unit in which it is defined. Thus, a statement
function name is not allowed to appear in an EXTERNAL statement and cannot be passed to
another procedure as an actual argument. The following example illegally attempts to pass the
statement function F to the subroutine SAM.
Example:
* Illegally passing a statement function
* to a subroutine.
PROGRAM MAIN
F(X) = X
.
.
.
CALL SAM( F )
.
.
.
END
2. If a statement function F contains a reference to another statement function G, then the
statement defining G must have previously appeared. In the following example, the expression
defining the statement function F illegally references a statement function G whose defining
statement follows the statement defining F.
Statement Functions 245