Language Elements
56
NetLinx Programming Language Reference Guide
Subroutines
A subroutine is a section of code that stands alone, and can be called from anywhere else in the program.
DEFINE_CALL subroutines
The DEFINE_CALL is the standard method provided by NetLinx for defining subroutines.
DEFINE_CALL '<subroutine name>' [(Param1,Param2,...)]
{
(* statements *)
}
where (Param1, Param2, ...) refers to a comma-separated list of <datatype><variable>
pairs. For example,
"INTEGER Size" would be one pair.
DEFINE_CALL names must not conflict with previously defined constants, variables, buffers, or wait
names. Unlike identifiers,
DEFINE_CALL names are case sensitive.
A subroutine may accept parameters. To do this, each parameter and its type must be listed within the set
of parentheses to the right of the subroutine name, as shown below:
DEFINE_CALL 'Read Input' (CHAR Buffer)[ ]
{
}
To invoke a user-defined subroutine, use the CALL keyword plus the name of subroutine and any
required calling parameters.
CALL 'Read Input' (Buf1)
In NetLinx, DEFINE_CALL supports the RETURN statement (as shown in the following example),
although return values are not supported.
DEFINE_CALL 'Read Input' (CHAR Buffer)
{
if (nChars = 0)
{
RETURN // exit subroutine
}
(* read input *)
}
SYSTEM_CALL subroutines
A SYSTEM_CALL subroutine is a special type of DEFINE_CALL subroutine defined in a separate
program file called a LIB file with a
PROGRAM_NAME entry matching the subroutine name.
PROGRAM_NAME = 'COSX'
DEFINE_CALL 'COSX' (FLOAT X)
{
(* body of subroutine *)
}
To invoke a system call, use the SYSTEM_CALL keyword followed by the name in single quotes and any
calling parameters, as shown below:
SYSTEM_CALL 'COSX' (45)
System calls are resolved automatically at compile time, without requiring an INCLUDE instruction to
include the system call source file.
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