Set difference (or nearest approximation)

What collection type / message should I use for set difference? I can't seem
to find any :-(

Sophie

2007/12/12, itsme213 <[hidden email]>:
> What collection type / message should I use for set difference? I can't seem
> to find any :-(

I do not understand what you mean with «set difference».

--
Damien Cassou

> What collection type / message should I use for set difference? I can't seem
> to find any :-(

#difference: ;-)

Lukas

--
Lukas Renggli
http://www.lukas-renggli.ch

just playing around:

(#(1 2 3) asSet) difference:  (#(1 2 3 4 5) asSet)                 a Set()
(#(1 2 3 9) asSet) intersection:  (#(1 2 3 4 5) asSet)           a Set(1 2 3)
(#(1 2 3 9) asSet) copyWithoutAll:  (#(1 2 3 4 5) asSet)      a Set(9)
(#(1 2 3 4 5) asSet) copyWithoutAll:  (#(1 2 3 9) asSet)      a Set(5 4)
(#(1 2 3 4 5) asSet) union:  (#(1 2 3 9) asSet)                    a Set(1 2 3 4 5 9)


I think you'dlike   aSet (4 5 9)

| set1 set2 difference |
set1 := #(1 2 3 9) asSet.
set2 := #(1 2 3 4 5) asSet.
difference := (set1 union: set2) copyWithoutAll: (set1 intersection: set2)


or
| set1 set2 difference |
set1 := #(1 2 3 9) asSet.
set2 := #(1 2 3 4 5) asSet.
difference := (set1 copyWithoutAll: set2) addAll: (set2 copyWithoutAll: set1)


That's just a quick try...

Cédrick

In mathematical language, you are expecting a symmetric difference, but
what people in the math dept I learned in usually mean by set difference
is what Squeak seems to be doing. Wikipedia seems to agree [1].


[1] http://en.wikipedia.org/wiki/Complement_%28set_theory%29


Daniel


cdrick wrote: