 Multiplication is often denoted by \(\,\cdot\,\). The recursive equation \(\,\cdot\, mn = Zm\textsf{I}(+n(\,\cdot\,(Pm)n))\) defines multiplication and it can be deciphered as “if \(m\) is \(0\) then the result is \(0\), else \(n\) is added to the result of \((m-1)\cdot n\).” The next step in the definition brings the right-hand side term to the form \(\textsf{X}\cdot mn\), where \(\textsf{X}\) does not contain occurrences of \(\,\cdot\,\), \(m\) or \(n\). Then taking the fixed point of \(\textsf{X}\), and setting \(\,\cdot\,\) to be \(\textsf{YX}\) concludes the definition of the multiplication function. For instance, the abstraction can yield the combinator