Here is what I mean. I have the following piece of code let theme = match theme with Some _ as x -> x | _ -> preferences#get_theme And I would like to replace it with this: let theme = Option.merge theme preferences#get_theme What should merge do is obvious. It returns the second argument if…

I do not see ~default argument being evaluated lazily. let value o ~default = match o with Some v -> v | None -> default I can do it with Option.fold but it seems overkill

Thanks @Chet_Murthy for suggesting the Monad Way. I’ve tried the let+ and it works but I will not call it an improvement. Judge for yourself let ( let// ) v f = match v with Some _ -> v | None -> f ();; let// x = Some 1 in Some 3 (* x is Some 1 *);; let// x = None in Some 3 (* x is Some 3 *);; …

There is an open PR to add let-operators to the OCaml Stdlib for the various monadic types.

Oh, now here’s another way to do this, that … seems syntactically more … “pleasant”? module OM = struct let (>>=) v f = match v with Some _ -> v | None -> Lazy.force f end ;; So you use it thus: # OM.( (Some 1) >>= lazy (Some 2)) ;; - : int option = Some 1 # OM.( None >>= lazy (Some 2)) ;; - : i…

Someone on here some time ago came up with a let|| (let-or) operator which I noted down at the time because it seemed quite interesting. It will accept the first option which does not evaluate to None. You can make the default the last value: let (let||) opt f = match opt with | Some _ -> opt…

[image] yawaramin: That was an interesting thread: Using let-binding syntax to implement option ‘or’ The fact that the (let||) operator automatically puts everything after the first binding into a thunk, and so on thereafter, is the nice part I think, because it gives you proper short-circui…

Yeah, it also lends itself nicely to resource handling: Downsides to calling Gc.full_major at exit?

I’m feeling this sort of … disquiet, that there’s no way to get this same functionality using infix operators. Let is fine for sure, but it seems unfortunate that there isn’t some way to have an infix operator that implicitly lazy-i-fies its right-hand-side argument, so that we can express short-ci…

Well that’s been a long-time OCaml philosophy, right? To be very explicit about everything. It’s only recently that we’re seeing some implicit behaviours start to come in to the language.

How do you feel about an Option.merge function in Stdlib?

Ecosystem

yawaramin April 26, 2020, 6:33pm 17

That was an interesting thread: Using let-binding syntax to implement option 'or'

Topic		Replies	Views
Using let-binding syntax to implement option 'or' Learning	3	1012	October 28, 2019
Option.fold with init taking a thunk Learning	12	748	February 27, 2023
Maybe monad in ocaml Learning	2	2307	July 25, 2022
Default of Option.value? Learning	1	288	May 8, 2024
Ocaml counterpart for `continue` and `return` in programming workflow Learning	5	448	July 13, 2023

How do you feel about an Option.merge function in Stdlib?

Related topics