Comment by bongobingo1 | Hacker News Reader

Comment by bongobingo1 | Hacker News Reader

I quite enjoy the idea of monadic types, and have written (beaten?) some into languages that dont have native support, but I cant help but wonder if this (and when I see rusts too) approach of `.if_then`/`ok_or` `.or_else` etc actually improve readability?

It always seems to best suit languages that have built in type/pattern matching and you actually design your functions to behave differently given a type vs obscuring what is nested if/else statements? (I know Rust can pattern match.)

I think there is some readability improvements when you're able to turn `if & if & if x | else | else | y` into `if & if & if x | y` by letting the empty type "fall out", but as soon as you have something like `if(if(x | y) | z)` the fall out nature has less effect.

> I cant help but wonder if this (and when I see rusts too) approach of `.if_then`/`ok_or` `.or_else` etc actually improve readability?

They can be mis/overused, but I think the declarative aspect and ability to split processing into clear steps makes them very helpful. They also allow "ignoring" the negative side or easily shunting values there, which may require repeated conditional checking (and obscure the actual processing) in a language without monadic operations.

They're also very compositional, so you don't have to update every API e.g. Java needs both a `Map#get` and a `Map#getOrDefault`, and that still doesn't really cover the case where the default is expensive to compute (so you want it to be lazy). In Rust, `Map::get` just returns an `Option`, and `Option` supports the relevant services (`unwrap_or` and `unwrap_or_else` in this case), which also means it supports those services for every API which returns an option.

In C++ they’re important for safety, because dereference of an empty std::optional is a silent UB. The methods robustly handle the checks for you.

Nested .map in Option or Result in Rust are indeed ugly, but the try operator (?) makes up for it in my opinion

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