=== Equivalent Expressions ===

When the expression can not be reduced further,
a list of equivalent expressions are displayed.

For example, type `(len . concat)(a, b)` and you will get the suggestion
`<=>  add((len · fst)(a)(b), (len · snd)(a)(b))`
Copy-paste this as the new input and it will reduce to `add(len(a))(len(b))`.
