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boundary=94eb2c0b176a61b5800532fa16f8 Subject: Re: [Caml-list] issue with polymorphism --94eb2c0b176a61b5800532fa16f8 Content-Type: text/plain; charset=UTF-8 Paging the type experts -- is there a concrete reason why we disallow writing this type directly? On Mon, May 16, 2016 at 1:32 PM, Gerd Stolpmann wrote: > Am Montag, den 16.05.2016, 17:55 +0100 schrieb Guillaume Hennequin: > > Thanks all for your prompt answers; > > > > > See the FAQ entry, "How to write a function with polymorphic > arguments?" > > > > https://ocaml.org/learn/faq.html#Howtowriteafunctionwithpolymorphicarguments > > > > this page explains how to do it with records or objects, but ends with a > > mysterious "FIXME: a direct way now exists". Does anyone know what this > might > > refer to? > > What you would need is > > let print_both : ('a . 'a -> 'a) -> unit = ... > > i.e. the scope of the quantifier is restricted to the first argument. > This doesn't exist to my knowledge. Maybe it was part of some dev > version? > > Gerd > -- > ------------------------------------------------------------ > Gerd Stolpmann, Darmstadt, Germany gerd@gerd-stolpmann.de > My OCaml site: http://www.camlcity.org > Contact details: http://www.camlcity.org/contact.html > Company homepage: http://www.gerd-stolpmann.de > ------------------------------------------------------------ > > --94eb2c0b176a61b5800532fa16f8 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Paging the type experts -- is there a concrete reason why = we disallow writing this type directly?
On Mon, May 16, 2016 at 1:32 PM, Gerd Stolpmann= <info@gerd-stolpmann.de> wrote:
Am Montag, den 16.05.2016, 17:55 +0100 schrieb Guillaume Henn= equin:
> Thanks all for your prompt answers;
>
> > See the FAQ entry, "How to write a function with polymorphic= arguments?"
> >=C2=A0 =C2=A0ht= tps://ocaml.org/learn/faq.html#Howtowriteafunctionwithpolymorphicarguments<= /a>
>
> this page explains how to do it with records or objects, but ends with= a
> mysterious "FIXME: a direct way now exists". Does anyone kno= w what this might
> refer to?

What you would need is

let print_both : ('a . 'a -> 'a) -> unit =3D ...

i.e. the scope of the quantifier is restricted to the first argument.
This doesn't exist to my knowledge. Maybe it was part of some dev
version?

Gerd
--
------------------------------------------------------------
Gerd Stolpmann, Darmstadt, Germany=C2=A0 =C2=A0 gerd@gerd-stolpmann.de
My OCaml site:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 http://www.camlcity.org<= br> Contact details:=C2=A0 =C2=A0 =C2=A0 =C2=A0 http://www.camlcity.= org/contact.html
Company homepage:=C2=A0 =C2=A0 =C2=A0 =C2=A0http://www.gerd-stolpmann.de=
------------------------------------------------------------


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