In OCaml, we can replace this code: let do_stuff1 () = let () = print_endline "Step 1" in let () = print_endline "Step 2" in let () = print_endline "Step 3" in print_endline "done" With this one: let do_stuff2 () = () ; print_endline "Step 1" ; print_endline "Step 2" ; print_endli…

It’s not a new idea, just never got much traction

I see now. It’s easier to understand with types. So you want a special operators for binding unit t monads. Well some people like to add all sorts of operators to their code. Personally, except for the established math ones, I think most operators tend to obscure rather than enlight and it’s bette…

Great find @monoidoid thanks. It looks like I’m referring to what alainfrisch refered to as @@@ then later as ;+ @dbuenzli yes I prefer not to use an operator if it is not conventional (most of the times). I just found that using the special let* syntax naturally leads you to wanting to define an o…

[image] benjamin-thomas: let ( & ) a b = let () = a in b You need to be careful with evaluation order of function arguments when you play these games. The evaluation order is not identical in native and byte code and in general it’s not a good idea to rely on evaluation order of arguments…

Interesting, thanks for letting me know. :thinking: Is this the reason why we can’t inspect the definition of semicolon? Meaning it behaves like a function but we can’t inspect its implementation nor override it. I deduce that it’s handled as a special case by the compiler?

[image] lindig: The evaluation order is not identical in native and byte code I’m fairly sure it’s meant to be. Do you have an example?

[image] benjamin-thomas: Is this the reason why we can’t inspect the definition of semicolon? Meaning it behaves like a function but we can’t inspect its implementation nor override it. It is not a function at all, and does not behave like one either. expr1; expr2 means “evaluate expr1, drop …

[image] vlaviron: It is not a function at all, and does not behave like one either. expr1; expr2 means “evaluate expr1, drop its result, then evaluate expr2”. On the other hand, expr1 & expr2 means "evaluate expr1 and expr2 in some undefined order, then call ( & ) on the results`. I had an im…

I wrote this based on memory and don’t have an example - I remembered (maybe wrong) that one would use left to right and the other right to left. In any case, it’s right to left for byte code, which still could be unexpected: utop # let f x y = ();; utop # f (print_endline "a") (print_endline "b");…

This is something that PPXes provide, and actually this is one of the reasons why I stick with PPXes providing monadic syntaxes rather than using let* and its friends. It is valid syntax to write let compute = res1;%x res2;%x res3;%x res4 or, in your style: let compute = () …

Let* syntax, semicolon and chaining units

Learning

lukstafi July 7, 2023, 3:05pm 15

See: Evaluation order - Learning - OCaml

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Let* syntax, semicolon and chaining units

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