Stop show with sound -- Keyboard shortcut: 'x'  Next slide in show -- Keyboard shortcut: 'n'  2 minutes, 51 secondsHigher-order Functions - slide 15 : 34

Reduction of a list by means of a binary operator transforms the list to a value in the range of the binary operator.

There is no natural value for reduction of the empty list. Therefore we assume as a precondition that the list is non-empty.