Defining global variables and constants

C modules may define global variables and constants. There are two different kinds of constants (symbolic and empty) that are useful in different contexts. The initialization of the value of an empty constant must happen in the Main function of the module, as described below.

Defining global variables

A_VAR(name)

Define a global variable with the specified name in the module. Its value will be initialized to nil.

See also: You may use the API functions AGetGlobalNum, ASetGlobalByNum, AGlobal and AGlobalByNum to set and query the value of the variable.

Defining constants

A_EMPTY_CONST(name)

Define a global constant with the specified name in the module. Its value will be initialized to nil. A constant with a nil value is mostly useless, so you can set the value of the constant using the two API functions ASetConstGlobalByNum and AGetGlobalNum.

Note: You must set the value of a constant only once in the Main function of the module that defined the constant.

Here is an example of defining a constant named Three with value 3:

static AValue Main(AThread *t, AValue *frame)
{
    int threeNum = AGetGlobalNum(t, "example::Three");
    frame[0] = AMakeInt(t, 3);
    ASetConstGlobalByNum(t, threeNum, frame[0]);
    return ANil;
}

A_MODULE(example, "example")
    A_EMPTY_CONST("Three")
    A_SUB("Main", 0, 1, Main)
A_END_MODULE()

A_SYMBOLIC_CONST(name)

Define a symbolic constant with the specified name in the module. Its value will be initialized to a std::Constant value, similar to using a global uninitialized const definition in Alore code. You must not try to change the value of a symbolic constant using ASetGlobalByNum or other means.