An exception raised when a function is invoked that is not defined.

For example:

# Let's use apply/3 as otherwise Elixir emits a compile-time warning
iex> apply(String, :non_existing_fun, ["hello"])
** (UndefinedFunctionError) function String.non_existing_fun/1 is undefined or private

The following fields of this exception are public and can be accessed freely:

• :module (module/0) - the module name
• :function (atom/0) - the function name
• :arity (non_neg_integer/0) - the arity of the function