Re: [Caml-list] issue with polymorphism

[Yotam Barnoy <yotambarnoy@gmail.com>]

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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 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
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> Company homepage:       http://www.gerd-stolpmann.de
> ------------------------------------------------------------
>
>

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