[M3devel] INTEGER

[hendrik at topoi.pooq.com]

On Thu, Apr 22, 2010 at 03:27:50PM -0400, Tony Hosking wrote:
> This is bizarre, and perverts the language definition significantly more than the current scheme.
> What is the base type of that subrange?

LONGINT.

-- hendrik

> 
> On 22 Apr 2010, at 10:55, hendrik at topoi.pooq.com wrote:
> 
> > On Thu, Apr 22, 2010 at 02:36:17PM -0400, Tony Hosking wrote:
> >> Let me see.
> >> 
> >> The green book definition says the base type of a subrange of INTEGER literals is INTEGER.
> >> You say that the base type of a subrange of LONGINT literals is LONGINT.
> >> But you say that LONGINT is not a defined type.  So, what is the type 
> >> of a LONGINT literal?
> > 
> > (a) 3849587394875493920398438483929293484L could very well be of type 
> > 3849587394875493920398438483929293484L..3849587394875493920398438483929293484L
> > which is a one-element subtype of LONGINT.
> > 
> > LONGINY is a type.  It's just one that's not available directly to the 
> > programmer.  It would not need to have a defined size, if the language 
> > allowed LONGINT values to occur *only* where an upper bound on 
> > their size is known, such as by being elements of a subrange.
> > 
> > -- hendrik
> > 
> >> 
> >> [I think I misunderstood you previously. I had interpreted that you meant LONGINT subranges to have base type INTEGER.]
> >> 
> >> On 22 Apr 2010, at 08:38, hendrik at topoi.pooq.com wrote:
> >> 
> >>> On Thu, Apr 22, 2010 at 11:57:16AM -0400, Tony Hosking wrote:
> >>>> But this is bizarre.  What type does an element of a subrange of 
> >>>> LONGINT have if not LONGINT?
> >>> 
> >>> It has LONGINT as a type.
> >>> 
> >>>> If the subrange has a base type of INTEGER then we need a mapping 
> >>>> between the elements of the subrange and the base INTEGER values.
> >>> 
> >>> Yes.  And INTEGER is different from the notion mathematicians have of 
> >>> integers in that there is a limit on the size of integers.  It's a 
> >>> machine or implementation-dependent limit, and it's imposed for 
> >>> efficiency reasons, but it's a specific limit just the same.
> >>> This limit is precisely what we're up against.
> >>> 
> >>>> But then, values of the LONGINT subrange don't have the same 
> >>>> representation as their INTEGER counterpart.
> >>> 
> >>> Of course not.  If they did have the same representation, there would be 
> >>> in-range for INTEGERs, and there would be no need to have LONGINT at 
> >>> all.
> >>> 
> >>> LONGINT is there precisely for the integers that *don't* fit in INTEGER.
> >>> 
> >>>> 
> >>>> All very odd.
> >>> 
> >>> But dictated by the intended use -- that of having integral ranges
> >>> whose bounds are dictated by the problem, not the hardware.
> >>> 
> >>> -- hendrik
> >> 
>