When I was writing java, I can place exn in function signature such as public Scanner(File source) throws FileNotFoundException; When I call this function without exception being catch import java.util.Scanner; import java.io.File; public class ScannerFromFile { public static void main(String[…

Exceptions in ocaml are not compile-time checked, i.e. it is not a compile time error to not handle exceptions. However, if you want similar functionality then use result/option data structures. A small lib to get you started is rresult - https://github.com/dbuenzli/rresult .

Thanks for your reply. I was wondering why not add exception check in compile-time? Does that make it compile more slower or something limit by the type system? I think such exception catch notification like java would help in large project.

[image] Taki: I was wondering why not add exception check in compile-time? Does that make it compile more slower or something limit by the type system? Hmm … not sure myself but I would guess it is the type system. I think such exception catch notification like java would help in large proj…

There’s also a lively discussion here: [image] Specific reason for not embracing the use of exceptions for error propagation? Ecosystem I don’t understand why one would not use exceptions to propagate errors in OCaml. The corresponding chapter in Real World OC…

It’s ok not to handle some exceptions. We need to raise an exception if we don’t know how to handle it on a particular level. If no level has such information (about how to handle an exception) - an exception will not be handled at all and that is fine. So this is my argumentation against your case.…

I believe there are difficuties with checked exceptions and higher-order functions. For example, how would you write the type for List.map if the function taken in the first parameter can throw an arbitrary exception? You’d end up having to use some generic exception annotation and lose the specific…

[image] Taki: I was wondering why not add exception check in compile-time? Does that make it compile more slower or something limit by the type system? I think we don’t need checked exceptions in OCaml like we do in Java because OCaml supports sum types (variants, polymorphic variants). In p…

Great thanks , that what I need. It seems that we could only choose one among Expressiveness(higher-order functions) and Safety(exhaustiveness checking)

[image] Taki: It seems that we could only choose one among Expressiveness(higher-order functions) and Safety(exhaustiveness checking) Note that this is not strictly true in the general sense; you can still achieve safety with sum types (variants) to represent your errors, as many have express…

Why not place exn in function signature?

Learning

bobbypriambodo April 13, 2018, 7:41am 5

There’s also a lively discussion here:

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Why not place exn in function signature?

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