# A polymorphic functional

Consider the following definitions :
Unset Implicit Arguments.
Definition compose (A:Set) (g f:A -> A) (x:A) := g (f x).
Definition thrice (A:Set) (f:A -> A) := compose A f (compose A f f).

Build an expression, the normal form of which is `27`, using
only two occurrences of `thrice`, one occurrence of `S`,
one occurrence of `(0)` and two jokers (symbol '`_`' ).

Same question, without using jokers.
## Solution

Look at this file

Going home

Pierre Castéran