Hi Levente,

On Mon, Oct 29, 2018 at 12:08 PM Levente Uzonyi <leves at caesar.elte.hu>
wrote:

>  On Mon, 29 Oct 2018, Eliot Miranda wrote:
>
> > Hi Chris,
> >
> >> On Oct 28, 2018, at 3:41 PM, Chris Cunningham <cunningham.cb at gmail.com>
> wrote:
> >>
> >> Looking at LargeIntegers (I'm 64 bit, so these are big):
> >> {
> >> 1152921504606846977 digitCompare:  -1152921504606846977.
> >> 1152921504606846977 digitCompare:  -1152921504606846978.
> >> 1152921504606846978 digitCompare:  -1152921504606846977.
> >> }  "#(0 -1 1)"
> >>
> >> {
> >> 1249 digitCompare: -1249.
> >> 1249 digitCompare: -1250.
> >> 1250 digitCompare: -1249.
> >> } #(1 1 1)
> >
> > this is correct.  The primitive is supposed to answer -1, 0 or 1
> depending on whether the (receiver digitAt: n) is <, =, or > the (argument
> digitAt: n) where n is either the first digit at which the receiver and
> argument differ or the last digit.  Since digitAt: does not answer the 2’s
> complement bit-anded SmallIntegers are not actually inconsistent
> >
> > -1 digitAt: 1 => 1
> > -1 digitAt: 2 => 0
> > 1 digitAt: 1 => 1
> > 1 digitAt: 2 => 0
> >
> > SmallInteger minVal - 1 digitAt: Smalltalk wordSize => 16 (64-bits) 64
> (32-bits)
> > SmallInteger maxVal + 1 digitAt: Smalltalk wordSize => 16 (64-bits) 64
> (32-bits)
> >
> > So the method needs a) a really good comment and b) a warning that this
> is private to the Integer hierarchy implementation and not for general use.
> >
> > It looks to me like the use in DateAndTime is a hack that works because
> LastClockValue is always +ve.
>
> I think DateAndTime >> #now:offset:'s comment gives a very good reason why
> #digitCompare: is used there. It doesn't go into details though.
>

Right. The comment states: "Ensure that consecutive sends of this method
return increasing values, by adding small values to the nanosecond part of
the created object. The next few lines are assumed to be executed
atomically - having no suspension points.".  Clever, Bert!
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