[M3devel] [Fwd: Re: A nonnative 64-bit language proposal]

[Darko]

I agree with you and I strongly agree with Tony's approach to the  
implementation where the two integer types are not subtypes.

The VAL usage would be a bit finicky given how often this would be  
done in practice, something more concise (like INT and LONG) would be  
better.


On 19/07/2007, at 11:20 PM, Rodney M. Bates wrote:

> In my original 64-bit proposal, I made INTEGER # LONGINT, and also  
> the two
> types have no subtype relation (which, I think is what Antony is  
> saying).
> It avoids having a lot of things happen implicitly from other rules  
> in the
> language.
>
> But then I added a separate rule that these two types and their  
> subranges
> are mutually assignable, subject to the existing assignability  
> rules that
> now apply to a type and its subranges. Namely the RHS value must be  
> in the
> range of the of the LHS type, which sometimes has to be checked at  
> runtime.
>
> This allows assignment without explicit conversion, as well as many  
> other
> things, for example, VALUE parameter passing, that require  
> assignability.
> This is consistent with the existing rules for assignments involving
> different subranges.
>
> For explicit conversions (which are probably needed somewhere anyway,
> even if not in assignments), VAL(v,LONGINT) and VAL(v,INTEGER) fit
> the existing language well.  For consistency, it seems good to allow
> ORD(LongIntArg), which is an alternative conversion in one direction.
> It may seem unnecessary, but it's not as useless as ORD(IntegerArg),
> which we already have.  Actually, these extensions of VAL and ORD
> fall out of the existing definitions, when LONGINT is an ordinal type.
>
> Darko wrote:
>> I actually favour a implicit conversion, which for this  
>> particular  case I think would be consistent with existing M3  
>> behaviour.
>> On 19/07/2007, at 10:26 PM, Tony Hosking wrote:
>>> This is a good question.  I would assume that conversion must be   
>>> explicit to fit with the M3 philosophy.  It would make sense to   
>>> have a conversion operation that performs the appropriate range   
>>> check?  Any ideas for a name for the operation.
>>>
>>> On Jul 19, 2007, at 4:23 PM, Darko wrote:
>>>
>>>> Have I missed something or is there no way to assign between   
>>>> INTEGER and LONGINT? Is there an explicit conversion function  
>>>> that  I've overlooked? Would assignment be so bad here since  
>>>> there would  be an implicit range check, much like when you  
>>>> assign between two  overlapping subranges? In a sense these two  
>>>> types are integer  subranges of an abstract integer type  
>>>> containing all integers.
>
> -- 
> -------------------------------------------------------------
> Rodney M. Bates, retired assistant professor
> Dept. of Computer Science, Wichita State University
> Wichita, KS 67260-0083
> 316-978-3922
> rodney.bates at wichita.edu