This package provides a canonical anonymous 1-tuple type missing from Haskell
for attaching typeclass instances.

NOTE: There is also the OneTuple package which by using a boxed data-type
provides a 1-tuple type which has laziness properties which are more faithful
to the ones of Haskell's native tuples; whereas the primary purpose of Only is
to provide the traditionally so named type-wrapper for attaching typeclass
instances.

WWW: https://github.com/haskell/Only