[Newbies] closed and open interval

[Randal L. Schwartz]

>>>>> "Bert" == Bert Freudenberg <bert at freudenbergs.de> writes:

Bert> On 24.11.2008, at 17:46, Randal L. Schwartz wrote:

>>>>>>> "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.

Bert> How so?

You're requiring the user to do their own encoding of "open = true, closed =
false", when that's really no business of the user.  And what if you decide
later to encode the four combinations as a single pluggable block or symbol?

-- 
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