Does Haskell have variables?

Question

I\'ve frequently heard claims that Haskell doesn\'t have variables; in particular, this answer claims that it doesn\'t, and it was upvoted at least nine times and accepted.<

Answer 1

Haskell has immutable variables (variables in the math sense) by default:

 foo x y = x + y * 2

By default variables are not mutable cells.

Haskell also has mutable cells though, but you enable them explicitly:

 > import Data.IORef (newIORef, readIORef, writeIORef)
 > v <- newIORef 0
 > readIORef v
 0

 > writeIORef v 7
 > readIORef v
 7

So, YES Haskell has true variables. But it does not use mutable variables by default.