List.Nonempty for Elm

A list that is known, at compile-time, to be nonempty. This means head and tail are guaranteed to succeed.

one = fromElement 2
two = 4 ::: one
toList two == [4, 2]
toList (dropTail) two == [4]
head two == 4
tail two == [2]

Testing

Run elm reactor in the test directory. Thanks to all the work that went into property-based testing, even if it's overkill for this tiny library.