Hello,

I'm writing an example (a message for calculating combinations out of a
collection and I found an amazing error. When line combOfRest :=
workList combinations: (n - 1) is called VM tries to evaluate things in
the self context (as if workList was self) and then x is nil and that
causes an error. Is this behavior expected?

I was expecting that workList combinations: x would be executed in a new
context (since it's an instance of IntegerArray)

By the way, when I inspect I discover that there are 3 instances of x
(one with right value, and two nil).

CdAB

    IntegerArray>>combinations: n
        "This message returns all possible combinations of n elements
    from self"
       
        | theCombinations workList |
       
        "First let's check conditions"
        n class ~= SmallInteger ifTrue: [ self error: 'argument should
    be SmallInteger but is: ',n class asString ].
        (n < 1 or: [ n > self size ]) ifTrue: [ self error: 'argument
    out of range: ',n asString ].
       
        theCombinations := OrderedCollection new.

        "Basic case #1: size equals to data size"
        n = self size ifTrue: [
            | x |
            x := OrderedCollection newFrom: self.
            theCombinations add: x.
            ^theCombinations ].

        "Basic case #2: size equals to 1"
        n = 1 ifTrue: [
            1 to: self size do: [ :i |
                | x |
                x := OrderedCollection with: (self at: i).
                theCombinations add: x ].
            ^theCombinations ].

        workList := self class newFrom: self.
       
        "Generic case"
        1 to: self size - n + 1 do: [ :i |
            | x combOfRest |
           
            x := workList at: 1.
           
            workList := workList allButFirst.
           
            *combOfRest := workList combinations: (n - 1)*.
           
            1 to: combOfRest size do: [ :j |
                (combOfRest at: j) add: x before: 1 ].
           
            theCombinations add: combOfRest ].
       
        ^theCombinations






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