Function exprtk_sys::symbol_table_add_func2

pub unsafe extern "C" fn symbol_table_add_func2(
    t: *mut CSymbolTable, 
    name: *const c_char, 
    cb: extern "C" fn(_: *mut c_void, _: c_double, _: c_double) -> c_double, 
    user_data: *mut c_void
) -> Pair<bool, *mut c_void>