[monadic2]

This is ridiculous: of course there are branches, but you don’t explicitly write them. This is purely aesthetic.

Edit: i simply wish the author illustrated why this is good or desirable—conditionals are not difficult to read.

[coldtea]

The aesthetic aspect is insignificant, it's about the semantics -- and thus reasoning about the code and other such properties. So nothing ridiculous about it.

It's like Haskell code "of course has" anything C has, as underneath the both run assembly instructions full of gotos and state manipulation, you just "don't explicitly write it".

[monadic2]

Do you have difficulty reasoning through conditionals?

Meanwhile the semantics of objects, especially one named “Output”, are super obvious and easy to reason about.

[egdod]

Branches aren’t hard to reason about though. The only* reason anyone cares about branches is that branch misprediction is expensive.

[BoiledCabbage]

I think branches are actually harder to reason about, we're just used to doing it since all of us have done it for so long. However I do believe that branches are less straightforward than "linear" code and add to mental complexity on larger projects.

Of course there is no data to back this up, but I think one of the next trends in programming beyond the adoption of functional styles, immutable data, "functional core / imperative shell" will be abstracting away from explicit conditional/branching logic in higher level code.

Obviously people can come up with pedantic/extreme cases where the abstraction does nothing to hide the complexity, or even makes things more complex but im not taking about that. I mean more simple abstractions like what was used in OP, or a filter() abstracting over a while and if combo.

I'm convinced based on personal experience that it makes for cleaner code and will become more widely adopted over the years as people explore it.

[egdod]

How is it possible to reason about filter() without thinking it through as effectively a conditional? How is that easier than being explicit about it?

[BoiledCabbage]

Why is separating pure functional code from imperative / side effect causing code easier to reason about? You still have to have the side-effect somewhere.

Why are immutable data structures easier to reason about? They still produce the same results.

None of the above are proven facts, but they are generally agreed upon principles that a number of people have observed. And I happen to believe them as well.

Overall my opinion of why it's easier is that like most optimizations it reduces the number of states/cases you have to think about in the "common path". With a solid abstraction you rarely need to think about the internals, with explicit code you need to check and think through all of the edge cases.

filter() (or map, or ...) is probably the best simple case I can think about. There is more room for bugs in an explicit (ex. for (int = 0; i < ...) {}) than in a filter over a collection / enumerable. When reading the code you need to think through base and termination conditions as well as confirm aggregation is happening correctly. With a filter() you don't have to do it / be explicit about it. Obviously you still need to know what filter means (which means you know it's implementation) but you don't need to focus on the details, only the filter condition: the signal amid the noise. The rest is pushed behind a solid reusable abstraction. Again thinking about it in isolation if someone just introduced the filter function to you you might look at it an say it really doesn't add much and if anything obscures my code I don't see the value. But after adopting it, and it's related family of monadic collection operations, code can now be written at a much denser, fewer off-by-one errors, higher signal to noise, level of abstraction. It's provided structure and common abstractions to unstructured iteration. To the point you begin to think in these abstractions (which I think is a benefit).

Another example are parser combinators. There is nothing that parser combinators do that can't be done by hand. But one of the primary way they simplify coding is by hiding away conditional (and looping logic). "?*.." , | and & concepts. Parser combinators also benefit in simplifying things by building an algebra for users to work in with nice closed operations. But again that only became possible by abstracting away the conditional and looping logic and making these nice simple abstractions that can be easily combined.

So my summary is, my view is that abstracting over control flow code does a lot to simplify logic. A lot of logic involving looping has already been abstracted over and included in languages and libraries (in general "functional programming" styles). Now that the low hanging fruit has been incorporated I think next will be the next layer of non-looping conditional logic.

[monadic2]

Why do you consider a conditional (I have no clue why you call it a “branch”, a semantically meaningless term at the language level) hard to reason about?

[BoiledCabbage]

Responded here: https://news.ycombinator.com/item?id=22186544