function pointers and callbacks

examples/interop/header/native.c

@@ -36,6 +36,17 @@ int imported_string(const char *value) {
 	return 0;
 }
 
+int imported_apply(Imported_Mapper mapper, int value) {
+	if (mapper == NULL) {
+		abort();
+	}
+	int result = mapper(value);
+	if (result != value * 2) {
+		abort();
+	}
+	return result;
+}
+
 int imported_variadic(int marker, ...) {
 	va_list args;
 	va_start(args, marker);