return func(set map[Elt]sets.Empty) Accumulator {
		var ans Accumulator
		for elt := range set {
			ans = reduceFn(ans, mapFn(elt))
		}
		return ans
	}
}

// SliceMapReduce is map-reduce starting from a slice.
func SliceMapReduce[Elt, Result, Accumulator any](mapFn func(Elt) Result, reduceFn func(Accumulator, Result) Accumulator) func([]Elt) Accumulator {
	return func(slice []Elt) Accumulator {
		var ans Accumulator