gotilty / gotil

func Reduce(a interface{}, f func(accumulator interface{}, val interface{}, i int) interface{}, accumulator interface{}) (interface{}, error) {

	val := reflect.ValueOf(a)

	switch val.Kind() {

	case reflect.Slice, reflect.Array:

		length := val.Len()

		index := -1

		newSlice := copySlice(a)

		if IsAssigned(accumulator) && length > 0 {

			index++

			accumulator = newSlice.Index(index).Interface()

		}

		index++

		for index < length {

			rowVal := val.Index(index)

			accumulator = f(accumulator, rowVal.Interface(), index)

			index++

		}

		return accumulator, nil

	}

	return nil, errs.NewUnsupportedTypeError(val.Kind().String())

}