Randal L. Schwartz wrote:
>>>>>> "Randal" == Randal L Schwartz <merlyn at stonehenge.com> writes:
> 
> Randal> Yes, that solves it for SequencableCollection, but not Collection.
> Randal> I think the trouble is how to solve it for the general case.
> 
> This may have been brought up before, but it just occurred to me
> that we merely need an "InjectionNull" class that answers the first
> argument in response to any message send, through a simple DNU handler.
> 
> Then we could implement #reduce: as:
> 
> reduce: aBlock
>   self ifEmpty: [^ some exception ].
>   ^self inject: InjectionNull new into: aBlock.

What about:

    | iteration |
    self ifEmpty: [ ^some exception ].
    iteration := [ :old :each | iteration := aBlock. each ].
    self do: [ :each | value := iteration value: value value: each ].
    ^value

Paolo