Returns the module that is a local root of all given modules. That is a common prefix of all given modules that is also a module from the list.

For instance, modules A and A.B have a common prefix that is A, and A is provided as an argument, so it will be returned.

But if only A.B and A.C are provided, the common prefix A will not be returned since it is not one of the arguments.

Examples

iex> local_root([A, A.B])
A

iex> local_root([A.B, A.C, A])
A

iex> local_root([A.B, A.C])
nil

iex> local_root([])
nil

@spec local_root(module(), module()) :: module() | nil

Given two module names, returns the module name that is a prefix of the other, or nil if the two names are disjoint.

See local_root/1.

Examples

iex> local_root(A, A.B)
A

iex> local_root(A.B, A.C)
nil