Comment by cerved
4 years ago
The point was that in map and reduce it's clear what's being done and what's being returned, especially in a typed language. Ideally you're also in an environment that doesn't allow for side effects, in which case, grandma gets no emails from map or reduce
It is not visible what is returned or what is input im case of chaining. Because return and input parameters are not directly visible and you have to read all previous calls to figure that out.
And they both trivially allow for side effects.