Is it possible to define fixity declaration in the REPL?

I love to play around in the REPL as it is a really fast and simple way of trying out new things. Certain aspects of the language is, as you know, done differently in the REPL as opposed to within modules, multi-line definitions being one of them.

Now, I wonder if, and in that case how, I can declare operator fixity in the REPL. The naive attempt...surprise...does not work.

Prelude> let (f · g) x = f(g(x))
Prelude> infixl 7 ·