interop.md

Functions and Interop

In Arcane, the scripting language does not support user-defined functions. Instead, you can call functions implemented in C via interop. When the interpreter encounters a function call, it performs a lookup in a table of interop functions (using function pointers) to execute the corresponding C function.

How It Works

1. Declaration:
   Declare the function in the header file (e.g., in arcane.h).

2. Definition:
   Implement the function in the source file (e.g., in functions.c).

3. Registration:
   Add an entry for the function in the interop_functions table.

Example: Adding the 'typeof' Function

Step 1: Declaration in arcane.h

Value fn_typeof(Value *args, int arg_count);

Step 2: Definition in arcane.c

Value fn_typeof(Value *args, int arg_count) {
    if (arg_count != 1) {
        fprintf(stderr, "Runtime error: typeof expects exactly one argument.\n");
        exit(1);
    }

    Value arg = args[0];
    const char *type_str = "unknown";

    switch (arg.type) {
        case VAL_INT:
            type_str = "int";
            break;
        case VAL_STRING:
            type_str = "string";
            break;
        case VAL_BOOL:
            type_str = "bool";
            break;
        case VAL_NULL:
            type_str = "null";
            break;
        default:
            break;
    }

    return make_string(type_str);
}

Step 3: Registration in the Interop Table

static Function interop_functions[] = {
    {"typeof", fn_typeof},
    // ...existing function entries...
};

By following these steps, any new C function you implement can be made available to Arcane scripts through the interop mechanism.

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