Open Watcom FORTRAN 77 Language Reference

Functions and Subroutines
12.6.1 ENTRY Statements in External Functions
Entry names may also appear in type statements. Their type may or may not be the same type as other
entry names or the actual name of the external function unless the function is of type CHARACTER. If the
function is of type CHARACTER then the type of all the entry names must be of type CHARACTER.
Conversely, if an entry name is of type CHARACTER, then all other entry names and the function name
must be of type CHARACTER. An entry name, like external function names, is treated as a variable within
the subprogram it appears. Within a function subprogram, there is an association between variables whose
name is an entry name and the variable whose name corresponds to the external function. When such a
variable becomes defined, all other such variables of the same type also become defined and other such
variables not of the same type become undefined. This can be best illustrated by an example.
Example:
PRINT *, EVAL(2), EVAL3(4.0)
END
INTEGER FUNCTION EVAL( X )
INTEGER EVAL2, X
REAL EVAL3, Y
C = 1
GOTO 10
ENTRY EVAL2( X )
C = 2
GOTO 10
ENTRY EVAL3( Y )
C = 3
10 EVAL2 = C * X
END
In the previous example, invoking EVAL would cause the result of 2 to be returned even though EVAL was
never assigned to in the function EVAL but since EVAL2 and EVAL are of the same type they are associated
and hence defining EVAL2 causes EVAL to be defined. However, invoking EVAL3 would cause an
undefined result to be returned since EVAL3 is of type REAL and EVAL2 is of type INTEGER and hence
are not associated. EVAL3 does not become defined.
12.6.2 ENTRY Statement Restrictions
1. An entry name may not appear in any statement previous to the ENTRY statement containing the
entry name except in a type statement.
2. If an entry name in a function is of type CHARACTER, each entry name and the name of the
function must also be of type CHARACTER. If the name of the function or the name of any
entry point has a length specification of (*), then all such entities must have a length
specification of (*) otherwise they must all have a length specification of the same integer
value.
3. If a dummy argument appears in an executable statement, then that statement can be executed
provided that the dummy argument is in the dummy argument list of the procedure name
referenced.
4. A name that appears as a dummy argument in an ENTRY statement must not appear in the
expression of a statement function unless it is a dummy argument of the statement function, it
has appeared in the dummy argument list of a FUNCTION or SUBROUTINE statement, or the
ENTRY statement appears before the statement function statement.
The ENTRY Statement 275