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Thu, 22 May 2014 02:01:01 -0700 (PDT) In-Reply-To: <537CD70F.9010503@ens-lyon.org> References: <762DAB52-9D2E-4002-80B0-526258DD7856@my.bristol.ac.uk> <2ABC1954-90FF-41CF-AB18-0C228A51CB8E@my.bristol.ac.uk> <537CD70F.9010503@ens-lyon.org> Date: Thu, 22 May 2014 10:01:01 +0100 Message-ID: From: Ben Millwood To: Martin Jambon Cc: David House , caml users , Ollie Frolovs Content-Type: multipart/alternative; boundary=001a11c136922d15ac04f9f95a83 Subject: Re: [Caml-list] Random.self_init in Jane Street Core --001a11c136922d15ac04f9f95a83 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 21 May 2014 17:40, Martin Jambon 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 ty= pe > annotation: > > $ ocaml > OCaml version 4.01.0 > > # ignore print_endline;; > Warning 5: this function application is partial, > maybe some arguments are missing. > - : unit =3D () > 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 >> > > 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 =E2=80=9Calias=E2=80=9D to Random.self_init was = assigned to >> nothing, so to speak, instead of calling the function. >> >> Many thanks, Dmitry! I=E2=80=99ve amended that line to let () =3D >> Random.self_init () and it works. >> >> On 21 May 2014, at 13:18, Dmitry Grebeniuk > > wrote: >> >> > Hello. >> > >> >> let _ =3D Random.self_init >> > >> > That's why I almost never use "let _ =3D ...", or >> > constrain "_" to some type when I use it. >> > Try to replace it with "let () =3D ..." and follow compiler >> > errors. Or with "let (_ : unit) =3D ...". >> >> >> -- >> Caml-list mailing list. Subscription management and archives: >> https://sympa.inria.fr/sympa/arc/caml-list >> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners >> Bug reports: http://caml.inria.fr/bin/caml-bugs >> >> >> > > > -- > Caml-list mailing list. Subscription management and archives: > https://sympa.inria.fr/sympa/arc/caml-list > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > Bug reports: http://caml.inria.fr/bin/caml-bugs > --001a11c136922d15ac04f9f95a83 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 2= 1 May 2014 17:40, Martin Jambon <martin.jambon@ens-lyon.org&g= t; 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:

=C2=A0 ignore (my_function foo);

Then this will start silently not calling [my_function] whenever
someone adds a second argument. You should instead use:

=C2=A0 ignore (my_function foo : Foo.t);

I think it used to be a problem but it no longer is. Recent versions of OCa= ml give a warning when passing a function, so there's no need for a typ= e annotation:

$ ocaml
=C2=A0 =C2=A0 =C2=A0 =C2=A0OCaml version 4.01.0

# ignore print_endline;;
Warning 5: this function application is partial,
maybe some arguments are missing.
- : unit =3D ()

You're right that t= his warning exists and mitigates the problem somewhat, but it doesn't s= ave you from the scenario where, say, a function changes from returning uni= t and throwing exceptions in the case of error to returning some error valu= e, 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 abo= ut.


On 21 May 2014 13:25, Ollie Frolovs
<ollie.frolovs.2012@my.bristol.ac.uk
<mailto:ollie.frolovs.2012@my.bristol.ac.uk>> wrote:

=C2=A0 =C2=A0 oh dear! i think i know what happened. self_init has never be= en
=C2=A0 =C2=A0 called in the first place! it requires a unit argument which = i did
=C2=A0 =C2=A0 not give it, so the =E2=80=9Calias=E2=80=9D to Random.self_in= it was assigned to
=C2=A0 =C2=A0 nothing, so to speak, instead of calling the function.

=C2=A0 =C2=A0 Many thanks, Dmitry! I=E2=80=99ve amended that line to let ()= =3D
=C2=A0 =C2=A0 Random.self_init () and it works.

=C2=A0 =C2=A0 On 21 May 2014, at 13:18, Dmitry Grebeniuk <gdsfh1@gmail.com
=C2=A0 =C2=A0 <mailto:gdsfh1@gmail.com>> wrote:

=C2=A0 =C2=A0 > Hello.
=C2=A0 =C2=A0 >
=C2=A0 =C2=A0 >> let _ =3D Random.self_init
=C2=A0 =C2=A0 >
=C2=A0 =C2=A0 > =C2=A0That's why I almost never use "let _ =3D = ...", or
=C2=A0 =C2=A0 > constrain "_" to some type when I use it.
=C2=A0 =C2=A0 > =C2=A0Try to replace it with "let () =3D ..." = and follow compiler
=C2=A0 =C2=A0 > errors. =C2=A0Or with "let (_ : unit) =3D ..."= .


=C2=A0 =C2=A0 --
=C2=A0 =C2=A0 Caml-list mailing list. =C2=A0Subscription management and arc= hives:
=C2=A0 =C2=A0 https://sympa.inria.fr/sympa/arc/caml-list
=C2=A0 =C2=A0 Beginner's list: http://groups.yahoo.com/group/oc= aml_beginners
=C2=A0 =C2=A0 Bug reports: http://caml.inria.fr/bin/caml-bugs





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