[Newbies] Re: closed and open interval

nicolas cellier ncellier at ifrance.com
Mon Nov 24 21:51:45 UTC 2008

Randal L. Schwartz a écrit :
>>>>>> "Filip" == Filip Malczak <filet00 at gmail.com> writes:
> Filip> You can always make subclass of Interval for example OpenedInterval , add
> Filip> two variables: left and right.Make new methods:
> OpenedInterval> from: aNumber to: aNumber left: aBoolean
> OpenedInterval> from: aNumber to: aNumber right: aBoolean
> OpenedInterval> from: aNumber to: aNumber left: aBoolean right: aBoolean
> You're exposing implementation there.  I suggest:
> beOpenLeft
> beClosedLeft
> isOpenLeft
> isClosedLeft
> and the corresponding "right" methods, rather than an explicit boolean.
> More flexibility later.

 > Gulik:
 > Actually, this works fine in the image already:
 > (1 to: Float infinity) includes: 1000   ---> true.
 > I didn't really expect it to work. Smalltalk is good like that :-).
 > Gulik.

Very nice that it works indeed. It was less obvious for this one:
     (1 to: Float infinity) includes: (10 raisedTo: 400).

Luckily, it does also work because of tricky IEEE policy:
     (Float infinity = Float infinity).
Above equality is far from obvious knowing:
     (Float infinity - Float infinity) isNan...
Don't know what they had in mind when comparing Infinities...

Anyway the Interval you proposed only has the cardinal of N.
Very small compared to the Cardinal of R required for [ 0 , 1 ].


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