#define REGISTER_FORMULA_FUNCTION(name, min_args, max_args, execute_body)                                              \
    class name##_function : public function_expression                                                                 \
    {                                                                                                                  \
    public:                                                                                                            \
        explicit name##_function(const args_list& args)                                                                \
            : function_expression(#name, args, ##min_args, ##max_args)                                                 \
        {                                                                                                              \
        }                                                                                                              \
                                                                                                                       \
    private:                                                                                                           \
        variant execute(const formula_callable& variables, formula_debugger* fdb) const                                \
        execute_body                                                                                                   \
    };

REGISTER_FORMULA_FUNCTION(debug, 0, 1,
{
    std::shared_ptr<formula_debugger> fdbp;
    bool need_wrapper = false;

    if(fdb == nullptr) {
        fdbp.reset(new formula_debugger());
        fdb = &*fdbp;
        need_wrapper = true;
    }

    if(args().size() == 1) {
        if(!need_wrapper) {
            return args()[0]->evaluate(variables, fdb);
        } else {
            return wrapper_formula(args()[0]).evaluate(variables, fdb);
        }
    } else {
        return wrapper_formula().evaluate(variables, fdb);
    }
})