Re: [Caml-list] Random.self_init in Jane Street Core

[Ben Millwood <bmillwood@janestreet.com>]

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On 21 May 2014 17:40, Martin Jambon <martin.jambon@ens-lyon.org> wrote:

> On Wed 21 May 2014 05:28:00 AM PDT, David House wrote:
>
>> Relatedly, one should be careful using the [ignore] function. Always
>> give its argument a type signature. E.g. if you do this:
>>
>>   ignore (my_function foo);
>>
>> Then this will start silently not calling [my_function] whenever
>> someone adds a second argument. You should instead use:
>>
>>   ignore (my_function foo : Foo.t);
>>
>
> I think it used to be a problem but it no longer is. Recent versions of
> OCaml give a warning when passing a function, so there's no need for a type
> annotation:
>
> $ ocaml
>        OCaml version 4.01.0
>
> # ignore print_endline;;
> Warning 5: this function application is partial,
> maybe some arguments are missing.
> - : unit = ()
>

You're right that this warning exists and mitigates the problem somewhat,
but it doesn't save you from the scenario where, say, a function changes
from returning unit and throwing exceptions in the case of error to
returning some error value, or vice versa. It seems just generally if the
return type of a function you use changes that's probably something you'd
want noise made about.


>> On 21 May 2014 13:25, Ollie Frolovs
>> <ollie.frolovs.2012@my.bristol.ac.uk
>> <mailto:ollie.frolovs.2012@my.bristol.ac.uk>> wrote:
>>
>>     oh dear! i think i know what happened. self_init has never been
>>     called in the first place! it requires a unit argument which i did
>>     not give it, so the “alias” to Random.self_init was assigned to
>>     nothing, so to speak, instead of calling the function.
>>
>>     Many thanks, Dmitry! I’ve amended that line to let () =
>>     Random.self_init () and it works.
>>
>>     On 21 May 2014, at 13:18, Dmitry Grebeniuk <gdsfh1@gmail.com
>>     <mailto:gdsfh1@gmail.com>> wrote:
>>
>>     > Hello.
>>     >
>>     >> let _ = Random.self_init
>>     >
>>     >  That's why I almost never use "let _ = ...", or
>>     > constrain "_" to some type when I use it.
>>     >  Try to replace it with "let () = ..." and follow compiler
>>     > errors.  Or with "let (_ : unit) = ...".
>>
>>
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>>
>
>
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