=== 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))`.

Equivalent expressions are used when there is not always clear which
direction to reduce an expression. This is hard-coded into the knowledge rule.
The decision of which rules should be reductions or equivalences is based on
Poi user experience over time. You can help improving the knowledge base!