Re: [Caml-list] Unary negation parsing

[Stanislav Artemkin <artemkin@gmail.com>]

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> In short, the literal maxint+1 is accepted because minint=-(maxint+1),
> and we don't have negative literals.

It looks strange that 4611686018427387904 is accepted (defect?), and OCaml
actually defines negative numeric literals according to
http://caml.inria.fr/pub/docs/manual-ocaml/lex.html

On the contrary, F# doesn't have negative numeric literals, but defines a
post-filtering of adjacent prefix tokens in 3.8.1. See
http://fsharp.org/specs/language-spec/3.0/FSharpSpec-3.0-final.pdf#page=28

Thanks

On Thu, Dec 3, 2015 at 12:49 AM, Gerd Stolpmann <info@gerd-stolpmann.de>
wrote:

> Thinking that this is a mostly aesthetic question, with one little
> exception:
>
> # max_int;;
> - : int = 4611686018427387903
> # -4611686018427387904;;
> - : int = -4611686018427387904
> # 4611686018427387904;;
> - : int = -4611686018427387904
> # 4611686018427387905;;
> Error: Integer literal exceeds the range of representable integers of
> type int
>
> In short, the literal maxint+1 is accepted because minint=-(maxint+1),
> and we don't have negative literals.
>
> However, the question is whether it is worth the trouble changing it. As
> you mention -safe-string, I just went through a large library and
> updated it, and it was far from trivial (needed GADTs) and a lot of work
> (something like 30 hours, really). I'm still skeptical whether changes
> of this kind get you a real benefit.
>
> Gerd
>
>
> Am Mittwoch, den 02.12.2015, 22:59 +0400 schrieb Stanislav Artemkin:
> > Hi all,
> >
> >
> > I've just stumbled upon yet another question about unary negation
> > parsing
> > (
> http://stackoverflow.com/questions/34044873/passing-negative-integer-to-a-function-in-ocaml
> ):
> >
> >
> > let f x = x + 1 in
> > f -1
> >
> >
> > is not valid in OCaml.
> >
> >
> > I'm just wondering why this issue is still not addressed in the
> > parser? For example, F# parses "f -1" as unary negation, but "f - 1"
> > and "f-1" as binary operator. It looks a bit tricky (as whitespace is
> > taken into account), but feels so natural when writing code.
> >
> >
> > Is there any reason we can't have the same in OCaml?
> >
> >
> > PS. I understand that it may break existing code, but it should be
> > solvable by a compiler option similar to -safe-string etc.
> >
> >
> > Thank you
> >
> >
>
> --
> ------------------------------------------------------------
> 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
> ------------------------------------------------------------
>

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