AbelianMonoid

Exports

• SumitType
  $0$:	%	zero
  $+$:	(%, %) $\to$ %	sum
  $*$:	(Integer, %) $\to$ %	product by an integer
  add!:	(%, %) $\to$ %	In-place sum
  zero?:	% $\to$ Boolean	test for $0$