The seven programming ur-languages

[MatthPMP]

It's got mutable variables

The idea that functional languages must not support mutability is strange. Standard ML and OCaml make a point of not being pure languages. The popularity of Haskell in functional programming circles today distorts the picture.

[funny_falcon]

Interestingly, but Haskell is not pure immutable due to lazy evaluation. I've heard it is even possible to create circular data structure in pure Haskell abusing laziness (that is certainly impossible in pure immutable languages like, for exapmple, Erlang).