[mpweiher]

Not sure what the "No" is about, because the rest is a restatement of what I wrote. Yes, they are transforming the value that's wrapped in an Either/Optional, just as I wrote, and yes, the map/flatMap is necessary due to that construction.

However, just as I also wrote, that's not an actual sequence of values, it's a single wrapped value (or none).

[appsappsapps]

The "no" was probably aimed at the fact that you were splitting hairs against their use of "sequence".

Optional can generally be thought of as a "sequence" of one or zero values. You could use an array of "[some]" or "[] /* none */" to manage control flow in an almost identical way (you'd just be adopting and managing an API that doesn't statically ensure that these arrays never have more than 1 value).

"map/flatMap" are predictable functions that can be used to manage the transformation of data (which is generally the entire point of code). The type/context that a computation is lifted into communicates a lot: Optional, for example, can be returned for a computation that may or may not return a value, and it can be "mapped" into another value by a pure computation that _always_ returns a value, or "flat-mapped" through a computation that may produce another nullable value. Anyone familiar with these basic functions can jump in, read the code, and generally know that every computation lifted into "map" can't fail, while every computation that is "flat-mapped" can. And in static languages it's all checked by the type system! No testing for "null" everywhere!