[ryandv]

> There's at least one other practical advantage as well, that of "chunking".

> When we have a grasp of relevant, powerful structures underlying our world, we can "chunk" along them to reason more quickly.

This is one thing I've observed about Haskell vs. other languages: it more readily gives names and abstractions to even the minutest and most trivial patterns in software, so that seemingly novel problems can be quickly pattern matched and catalogued against a structure that has almost certainly been seen before.

One example: I want to run two (monadic) computations, and then somehow combine together their results (with some binary operation). Such a trivial and fundamental mode of composition, that seems to lack a name in almost every other programming language. Haskell has a name for this mode of composition, and it's called liftM2.

Never again will you have to re-write this pattern for yourself, leaving yourself open to error, now that you have this new concept in your vocabulary. Other languages will happily let you reinvent the wheel for the umpteenth time, or invent idiosyncratic patterns and structures without realizing that they are just particular applications of an already well-studied and well-worn concept.

[maleldil]

Note that this is general enough that you don't need a Monad for this. Applicative is enough (liftA2).

[solomonb]

Not if you need to perform two /Monadic/ operations as the commenter stated explicitly.

[tel]

Every monad is also an applicative and liftA2 does/is the same thing as liftM2. The only reason they both exist was due to Monad being popularized in Haskell earlier than Applicative and thus not having it as a superclass until the Functor-Applicative-Monad Proposal in Haskell 2014. It was obviously correct, but a major breaking change that also got pork barreled a bit and so took a while to land.

[solomonb]

Yes you're absolutely right. I had a bit of a brain fart moment here. If they were Applicative operations then you would not be able to use `liftM2`, not the other way around.

[mnsc]

This is my fear when I think about doing actual in a team using a functional language. That there's an imbalance in understanding between participants in a team making all discussions about problem x into the pattern matchning problem y. Like "is this liftM2 or liftA2?"

I've only had a couple of months of experience working with scala before the team switched to Java. The reasons were many but one of them was that the external consultant that was most knowledgeable in "thinking with functions" was kind of a dick. Making onboarding into a horror show of "go look up yt video x before I can talk about this functionality" with a condescending tone. So within a month he was let go and then no one in the remaining team really had the courage to keep debe it further. Some thought that they maybe could maintain the current functionality but the solution was only like half complete. (in the consultant mind it was complete because it was so generic you only needed to add a couple of lines in the right place to implement each coming feature)

That said, I would love to work in a hardcore Haskell project with a real team, one with a couple of other "regular" coders that just help each other out when solving the actual problems at hand.

[solomonb]

Well, I can't speak to your experience but in the case of liftM2 vs liftA2 I have never even seen liftM2 get used. Its more of a historical oddity that it is available.