Exceptions basically mean "runtime error".  This is why some APIs use
the result type instead of exceptions.  So the API could be something
like:

val int_of_string : string -> (int, err) result

where err is some error type.

I wrote a blog post about this years ago, the APIs in it might be out
dated but the general concept is probably still applies:

http://functional-orbitz.blogspot.se/2013/01/experiences-using-resultt-vs-exceptions.html

Lorenzo Pomili <lorenzo.pomili85@gmail.com> writes:

> Friend of mine, pointed out to me a case in Reason who cause no compile
> time error but run time error, I had reimplemented similar case in OCaml:
>
>
>
> exception Generic_exc;;
>
> let string_of_string s = string_of_int (int_of_string s)
>
> let foo = string_of_string "foo"
>
> let fun_exeption x =
>     match x with
>     0 -> 0
>     | _ -> raise Generic_exc
> ;;
>
> let bar = string_of_int (fun_exeption 5)
>
>
>
> both foo and bar don't fail at compile time fail at run time, me and my
> friend also try to reimplement similar case (the first one with string and
> int) in Elm, and Elm compiler just say you have to manage exeption, because
> function can actualy return exeption instead of int.
>
> There is a compile params or similar for check this kind of error? is a
> side effect of have a multi-paradigm? and if is it, how to manage it?
>
> I belive I can use OCaml in functional way without just making attention to
> not use side effect but if use of function like int_of_string can make run
> time error, I probably approac to OCaml in wrong way, and I wanna
> understand how to correct it.