Language Elements
57
NetLinx Programming Language Reference Guide
For special cases where multiple copies of a system call are needed, an instance number can be specified
in the call. The compiler will compile a separate copy of the subroutine for each system call instance
number. For example, the following commands force the compiler to include two separate copies of
COSX:
SYSTEM_CALL[1] 'COSX' (45)
SYSTEM_CALL[2] 'COSX' (60)
This technique could be useful in cases where a system call contains a wait instruction that conflicts
when multiple calls to the same subroutine were made during a single wait period.
Function Subroutines
A function is similar to a DEFINE_CALL, but is intended for use either standalone or in-line as an
expression. Instead of requiring a string literal for its name, it requires a name that follows the rules for
naming constants and variables. This eliminates the need for using the
CALL keyword to invoke the
subroutine.
DEFINE_FUNCTION subroutines also differ from DEFINE_CALL by allowing values to be
returned using the
RETURN statement (see below).
Syntax:
DEFINE_FUNCTION [<return type>] FnName[(Param1,Param2,...)]
{
(* statements *)
}
Example:
DEFINE_FUNCTION INTEGER myFunction (INTEGER Var0)
{
INTEGER nBytes
STACK_VAR RESULT
nBytes = 0
RETURN = Var0 + nBytes
RETURN RESULT
}
The DEFINE_FUNCTION subroutine can be called as a single programming statement. For example,
the following syntax:
The return type may only be one of the 8 intrinsic types. Strings, arrays, structures,
classes and other user-defined types may not be returned.
You cannot declare and initialize variables in the same line.
You must group the declarations first, followed by the initialization.
When it is a NetLinx function, a syntax where there appears a ([ ]), the ( ) are NOT
OPTIONAL but the [ ] are optional.
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