> you could make a generic `map` function that worked on any container type. not only container types, it can be any type that has a consistent context of eval

> you could make a generic `map` function that worked on any container type. not only container types, it can be any type that has a consistent context of evaluation for the final value being calculated: "doing async IO", "doing optional presence", "doing potentially erroneous extraction", and so on. In that sense, "doing multiplicity of values" is the context expressing a container type you mentioned as an example.