Only the first function in a file, the one with the same name as the file, can be directly referred to by another file; that second file just needs to refer to the first one by name when the first one is on the path.
Any other functions in a file can only be referenced by way of a function handle somehow provided by the first function in a file. For example, the first function could return a structure of function handles that could then be used by in another routine.
