Function define_function_full 

pub fn define_function_full(
    map: &mut HashMap<&'static str, FunctionSpec>,
    names: &[&'static str],
    node_type: &'static str,
    num_args: usize,
    num_optional_args: usize,
    arg_types: Option<Vec<ArgType>>,
    allowed_in_argument: bool,
    allowed_in_text: bool,
    allowed_in_math: bool,
    infix: bool,
    primitive: bool,
    handler: FunctionHandler,
)