monadic

In practice, the monadic parts of your code will end up associated with particular tasks that lend themselves to the monadic style.

Follow-on question, are there any useful monadic constructs not tied to collections (including optional as you said)?

You use the monadic parts when you need to abstract over it, just like with generics.

You cannot easily convert between functional and monadic style without a radical restructuring of code.

Option and Optional are indeed monads, and Java's Optional.flatMap() function is the monadic /bind/ function.

It's difficult to interface with procedural code, since your monadic code must be pure.

I guess it depends on your definitions, but monadic state is just as explicit as any other.

Let's pick a type which happens to be monadic, though, like list.

It's possible to implement a Monad that doesn't obey the monadic laws.

In order to follow the laws, one bit of important information is an idea of sequence or nesting—but one unique to each particular monadic triple.

You must be able to call pure functions on these monadic values without the side state seeping into the function (it has the bind function).

It's really the add function, strangely, which is monadic here.

But you need to start stretching your imagination to see why "andThen" makes sense for other monadic types.

Monads are really just a small set of functions that operate in a certain way (that "satisfies the monadic laws") on a type.

Elm uses "andThen" instead of "bind", which works pretty well for the monadic types in its core library.

"You must be able to call pure functions on these monadic values without the side state seeping into the function (it has the bind function)." That sounds more like fmap.

Monadic syntax (for/yield) makes it easy to compose state changes that should happen atomically, and since the call to actually perform the modification is explicit, it's easy to see which changes are atomic and which are not.

Monadic code in Swift has a few problems.