Kernel.is_function
You're seeing just the function
is_function, go back to Kernel module for more information.
Specs
Returns true if term is a function; otherwise returns false.
Allowed in guard tests. Inlined by the compiler.
Specs
is_function(term(), non_neg_integer()) :: boolean()
Returns true if term is a function that can be applied with arity number of arguments;
otherwise returns false.
Allowed in guard tests. Inlined by the compiler.
Examples
iex> is_function(fn x -> x * 2 end, 1)
true
iex> is_function(fn x -> x * 2 end, 2)
false