# Unfolding Fix

In pure lambda calculus (untyped or typed) the `fix`

combinator is used to encode recursion. `fix`

represents the least fixed point of a function `f`

i.e the least defined `x`

for which `f x = x`

. An important concept is that a function **need not have a least fixed point**. But for those functions which do, the least fixed point is the base case for recursion. An intuition about the least fixed point is :