Combines two T instances associatively.
Combines two T instances associatively.
result of combining l and r
Returns an instance of T calculated by summing all instances in
iter in one pass.
Returns an instance of T calculated by summing all instances in
iter in one pass. Returns None if iter is empty, else
Some[T].
instances of T to be combined
None if iter is empty, else an option value containing the summed T
Returns the identity element of T for plus.
Returns the identity element of T for plus.
This Monoid allows code to depend on the result of computation asynchronously. This is a slightly less general version of the TunnelMonoid. See the documentation for TunnelMonoid for general motivation. NOTE: the Promise will be fulfilled with the value just before the PromiseLink is calculated.