[CakeML-dev] [CakeML-Dev] targeting word literal constructors in AST

[Ramana Kumar]

(Minor correction, it was ``WordFromInt W8`` rather than ``W8FromInt``.)

Another more straightforward suggestion is concrete syntax directly
corresponding to the AST literals, e.g.:
8w3 -> Word8 0w3
64w3 -> Word64 0w3
The problem here is that it's not SML compatible. However, we could
additionally have 0w3 mapping to the 64-bit version.

On 29 November 2016 at 09:57, Ramana Kumar <Ramana.Kumar at cl.cam.ac.uk>
wrote:

> Good point, Michael. I didn't think about the problem of redefining
> int_to_word or Word8.fromInt - that makes targeting them in the parser seem
> less appealing to me. (However, note that my suggestion did not involve
> targeting Word8.fromInt from the parser.)
>
> Scott: my suggestion was to parse "0w3" as ``Word64 0w3`` and not have
> special Word8 literals. To write programs with word8s, you must use
> Word8.fromInt from the basis library (which maps to the primitive
> ``W8FromInt``).
>
> On 29 November 2016 at 09:41, Scott Owens <S.A.Owens at kent.ac.uk> wrote:
>
>> I don’t think my suggestion is that weird. The semantics of the language
>> would change so that int_to_word as a name has a special, explicitly
>> documented meaning. You could require that any definition of int_to_word
>> has to have type int -> WordN.t for some N IN {8, 32, 64} or something like
>> that, to catch the error at a better location. I didn’t really understand
>> Ramana’s suggestion.
>>
>> Scott
>>
>> > On 2016/11/28, at 22:24, Michael.Norrish at data61.csiro.au wrote:
>> >
>> > The other idea I had, which would at least allow the parser to target
>> the AST (suggestions below would suggest we drop one or both of the
>> Word{8,64} constructors), was to have 0w3 go to Word8, and 0W3 go to Word64…
>> >
>> > Scott’s suggestion is pretty weird incidentally, it would mean that
>> inserting
>> >
>> >   fun int_to_word x = x
>> >
>> > in a program that doesn’t contain that string anywhere could cause it
>> to fail to typecheck.  I mildly prefer Ramana’s because to get the
>> comparable problem there, you’d have to insert the slightly more involved
>> >
>> >   structure Word8 = struct fun fromInt i = I end;
>> >
>> > which would break pieces of code with no textually apparent references
>> to Word8.
>> >
>> > Michael
>> >
>> > From: Ramana Kumar <Ramana.Kumar at cl.cam.ac.uk>
>> > Date: Monday, 28 November 2016 at 20:29
>> > To: Scott Owens <S.A.Owens at kent.ac.uk>
>> > Cc: "Norrish, Michael (Data61, Canberra City)" <
>> Michael.Norrish at data61.csiro.au>, "developers at cakeml.org" <
>> developers at cakeml.org>
>> > Subject: Re: [CakeML-dev] [CakeML-Dev] targeting word literal
>> constructors in AST
>> >
>> > I like Scott's suggestion.
>> >
>> > On 28 November 2016 at 20:23, Scott Owens <S.A.Owens at kent.ac.uk> wrote:
>> > Or we could have the parser map 0w3 to something like “int_to_word 3”
>> and leave it in the programmers control, and have the basis start with a
>> default.
>> >
>> > Scott
>> >
>> > > On 2016/11/28, at 07:36, Ramana Kumar <Ramana.Kumar at cl.cam.ac.uk>
>> wrote:
>> > >
>> > > I doubt we want to go down that path...
>> > >
>> > > Here's a (somewhat random) suggestion: word literals (0w3 etc.) are
>> mapped to Word64.word, and to get bytes via parser you need to use
>> Word8.fromInt.
>> > >
>> > > On 28 November 2016 at 15:35, <Michael.Norrish at data61.csiro.au>
>> wrote:
>> > > Presumably SML allows type inference to figure out the width in the
>> same way that numeric operations get overload-resolved:
>> > >
>> > >
>> > >
>> > > (* Poly/ML *)
>> > >
>> > > > Word8.+(0w3, 0w4);
>> > >
>> > > val it = 0wx7: Word8.word
>> > >
>> > > > Word64.+(0w3, 0w4);
>> > >
>> > > val it = 0wx7: Word64.word
>> > >
>> > >
>> > >
>> > > Michael
>> > >
>> > >
>> > >
>> > > From: Ramana Kumar <Ramana.Kumar at cl.cam.ac.uk>
>> > > Date: Monday, 28 November 2016 at 11:46
>> > > To: "Norrish, Michael (Data61, Canberra City)" <
>> Michael.Norrish at data61.csiro.au>
>> > > Cc: "developers at cakeml.org" <developers at cakeml.org>
>> > > Subject: Re: [CakeML-Dev] targeting word literal constructors in AST
>> > >
>> > >
>> > >
>> > > SML does not distinguish syntactically. I guess we might have to
>> invent some syntax...?
>> > >
>> > >
>> > >
>> > > On 28 November 2016 at 11:03, <Michael.Norrish at data61.csiro.au>
>> wrote:
>> > >
>> > > There are both Word8 and Word64 constructors for word literals in the
>> AST type. How are the parser or lexer meant to figure out which any piece
>> of syntax corresponds to?
>> > >
>> > > Michael
>> > >
>> > > _______________________________________________
>> > > Developers mailing list
>> > > Developers at cakeml.org
>> > > https://lists.cakeml.org/listinfo/developers
>> > >
>> > >
>> > >
>> > >
>> > > _______________________________________________
>> > > Developers mailing list
>> > > Developers at cakeml.org
>> > > https://lists.cakeml.org/listinfo/developers
>> > >
>> > >
>> > > _______________________________________________
>> > > Developers mailing list
>> > > Developers at cakeml.org
>> > > https://lists.cakeml.org/listinfo/developers
>> >
>> >
>> > _______________________________________________
>> > Developers mailing list
>> > Developers at cakeml.org
>> > https://lists.cakeml.org/listinfo/developers
>>
>> _______________________________________________
>> Developers mailing list
>> Developers at cakeml.org
>> https://lists.cakeml.org/listinfo/developers
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cakeml.org/pipermail/developers/attachments/20161129/c69e1099/attachment.html>