[Haskell-cafe] [] vs [()]

[John Dorsey]

> dmehrtash:
> >    What is the difference between empty list [] and list with one unit
> >    element [()]?
> 
>     Prelude> length []
>     0
>     Prelude> length [()]
>     1

Also, they differ in type.

[()] is a list of unit elements, and happens to contain exactly one
of them.

[] is a (polymorphic) list of any kind of element, and happens not to
contain any of them.

Regards,
John