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where
Pull is a monad in the returned type, and can be used for stateful streaming, and Stream is a monad in the emitted type, and can be used for control flow
and conceptually
Stream f a = Pull f a ()
when I started with fs2 the existence of both
Stream and Pull seemed like a wart (although at the time it was obscured by a bunch of other stuff like Handle), but in truth it's one of the best design decisions of the whole library
my writings have a bunch of long-ish explanations (for lack of a more structured resource, sorry) http://systemfw.org/writings
the tl;dr is that it's a fancy iterator, just built as an algebra rather than side-effecty interface
oh, that's interesting, i didn't realize that a lot of the links point back to gitter. great idea!
I also wrote up a thing about Pull
that I think helps drive home the "iterator" aspect
I worry more about gitter getting shutdown at brief notice
At least gitter is indexed on google
Some option to grab archives from there
https://typelevel.org/cats/datatypes/either.html#solution-2-adts-all-the-way-down talks about error ADTs, what's SOP for common errors that you want to share across modules?
but it's not worth writing it differently than what you have I don't think
you can notice by changing
(A, B) => C into A => B => C
then factorising the whole signature into
(A => B) => (A => (B => C)) => (A => C)
then abstracting
A => into F[_]
F[B] => F[B => C] => F[C]
and then alfa-rename and switch order into
F[A => B] => F[A] => F[B], which is the key signature of the Apply typeclass
(renamed some type variables for clarity)
in particular the starting point could have have swiping
f and g and noticing basically (A => B) => (A => C)
that should trigger your functorial warning, since functor, applicative and monad can all be seen to transform things into
F[B] => F[C]
although it's easier to rename things to
F[A] => F[B] for consistency with the way things are usually written down
map: (A => B) => (F[A] => F[B])
ap: F[A => B] => (F[A] => F[B])
flatMap: (A => F[B]) => (F[A] => F[B])
which also helps with understanding that the real difference between power in the three typeclasses reflects the difference in power between
A => B (uneffectful), F[A =>B](effectful but no context sensitivity) and A => F[B] (the effect can depend on the output of the previous computation, since A => F
I'll tell that to my manager when he starts about communication and presenting
ahahhaha :+1:
(kind of like flatMap wooo)
https://typelevel.org/cats/datatypes/either.html#solution-2-adts-all-the-way-down talks about error ADTs, what's SOP for common errors that you want to share across modules?
i think usually you have a separate ADT that is shared across modules. if you can have direct dependencies, then the upper ADT can refer directly to the module error types. otherwise you can cast or translate the module errors into something like Throwable which the upper ADT wraps
you probably don't need it, and it's more complicated, but you could have a typeclass that translates "lower" level errors into a "higher" level error, but that means the higher level error loses information (which may be ok)