Product package:constrained-categories

The product function computes the product of the numbers of a structure.

Examples

Basic usage:

>>> product []
1

>>> product [42]
42

>>> product [1..10]
3628800

>>> product [4.1, 2.0, 1.7]
13.939999999999998

>>> product [1..]
* Hangs forever *

It is fairly common for functors (typically, container-like) to map Either to tuples in a natural way, thus "separating the variants". This is related to Foldable (with list and tuple monoids), but rather more effective.

sum2product ≡ mapEither id