Binding C Functions

Whether you're embedding Kuroko in an application or writing an extension module, binding a C function is something you'll want to do.

The Easy Way

#include <kuroko/kuroko.h>
#include <kuroko/vm.h>
#include <kuroko/util.h>
 
KRK_Function(myfunction) {
    FUNCTION_TAKES_EXACTLY(1);
    CHECK_ARG(0,int,krk_integer_type,myarg);
    return INTEGER_VAL(myarg*myarg);
}
 
int main(int argc, char *argv[]) {
    krk_initVM(0);
    BIND_FUNC(vm.builtins, myfunction);
    krk_startModule("__main__");
    krk_interpret("print(myfunction(42))","<stdin>");
    krk_freeVM();
    return 0;
}

This demo uses the utility macros provided in <kuroko/util.h> to easily create a function with argument checking and bind it to the builtin namespace.

KRK_Function() takes care of the function signature and function naming for exception messages.

FUNCTION_TAKES_EXACTLY() provides simple argument count validation. FUNCTION_TAKES_AT_LEAST() and FUNCTION_TAKES_AT_MOST() are also available.

CHECK_ARG() validates the type of arguments passed to the function and unboxes them to C types.

INTEGER_VAL() converts a C integer to a Kuroko int value.

BIND_FUNC() binds the function to a namespace table.

The Hard Way

While the macros above provide a convenient way to bind functions, they are just wrappers around lower-level functionality of the API.

#include <kuroko/kuroko.h>
#include <kuroko/vm.h>
 
static KrkValue myfunction(int argc, KrkValue argv[], int hasKw) {
    int myarg;
 
    if (argc != 1) return krk_runtimeError(vm.exceptions->argumentError, "myfunction() expects exactly 1 argument, %d given", argc);
    if (!IS_INTEGER(argv[0])) return krk_runtimeError(vm.exceptions->typeError, "expected int, not '%T'", argv[0]);
 
    myarg = AS_INTEGER(argv[0]);
 
    return INTEGER_VAL(myarg*myarg);
}
 
int main(int argc, char *argv[]) {
    krk_initVM(0);
    krk_defineNative(&vm.builtins->fields, "myfunction", myfunction);
    krk_startModule("__main__");
    krk_interpret("print(myfunction(42))", "<stdin>");
    krk_freeVM();
    return 0;
}