Skip to content

Local Variables

Local variables are restricted in scope to the statement block in which they are declared. A statement block is one or more NetLinx statements enclosed in a pair of braces, like the blocks following subroutines, functions, conditionals, loops, waits, and so on.

Local variables must be declared immediately after the opening brace of a block but before the first executable statement. To provide compatibility with the Axcess language, local variables may be declared right before the opening brace for DEFINE_CALL declarations only. For example, both formats shown below are legal in the NetLinx language:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
DEFINE_CALL 'My Subroutine' (INTEGER INT1)
LOCAL_VAR INTEGER INT2
{
    (* body of subroutine *)
}

DEFINE_CALL 'My Subroutine' (INTEGER INT1)
{
    LOCAL_VAR INTEGER INT2
    (* body of subroutine *)
}

The scope of a local variable is restricted to the statement block in which it is declared. A local variable is either static or non-static, depending on whether it is declared as LOCAL_VAR or STACK_VAR:

  • The keyword LOCAL_VAR specifies a static variable. A static variable's value is initialized the first time the statement block in which it is declared is executed and retained after execution of the statement block has finished.
  • The STACK_VAR keyword specifies a non-static variable. A non-static variable's value is re-initialized every time the statement block in which it is declared is executed.
  • If neither the LOCAL_VAR nor the STACK_VAR keyword is specified, STACK_VAR is assumed (default).

Example:

1
2
3
4
5
6
IF (X > 10)
{
    LOCAL_VAR INTEGER INT2  // static (permanent)
    STACK_VAR CHAR ARRAY1[10] // non-static (temporary)
    (* statements *)
}

LOCAL_VAR and STACK_VAR can be used interchangeably in any statement block except for waits. Only LOCAL_VAR variables may be declared inside a wait block.

Example:

1
2
3
4
5
WAIT 10, 'My Wait Name'
{
    LOCAL_VAR CHAR TempBuf[80]
    (* statements *)
}

A name assigned to a local variable must be unique within the statement block in which it is declared and any statement block enclosing that block. Therefore, non-nested statement blocks can define the same local variable name without conflict.

Example:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
DEFINE_FUNCTION integer MyFunc(INTEGER nFlag)
{
    LOCAL_VAR INTEGER n

    IF (nFlag > 0)
    {
        LOCAL_VAR INTEGER n  // illegal declaration
        .
        .
    }
    .
    .
}

DEFINE_FUNCTION integer MyFunc(INTEGER nFlag)
{
    IF (nFlag > 0)
    {
        LOCAL_VAR INTEGER n
        .
        .
    }
    else
    {
        LOCAL_VAR INTEGER n  // legal declaration
    }
}

If a local variable shares the same name as a global variable, the local variable always takes precedence.

The general form of a static local variable declaration is:

1
2
[LOCAL_VAR] [VOLATILE | PERSISTENT] [CONSTANT]
[<type>] name [= <value>]

The general form of the non-static local variable declaration is:

1
[STACK_VAR] [<type>] name [= <value>]

Since non-static local variables are allocated on the program stack (a block of memory reserved for allocation of temporary variables), the keywords VOLATILE, PERSISTENT and CONSTANT do not apply.

See Also