[squeak-dev] Collection>>sum implementation

> Colin Putney wrote:
>>
>> This is  a bit like the #join: debate that comes up every now and then
>> when a Ruby/Python/Perl ex-pat asks how it is that we don't have  a method
>> for joining an array of strings into a single string. The short answer is
>> that it's because #join: only makes sense when all the elements of a
>> collection are strings, and therefore, it's bad design.
>
> I have to disagree. Have you ever looked at the senders of do:separatedBy:
> (which is the easiest way to find lots the places that would be improved by
> join)? For example:
>
> ClassDscription>>instanceVariablesString
>  "Answer a string of my instance variable names separated by spaces."
>  ^String streamContents: [ :stream |
>    self instVarNames
>      do: [ :each | stream nextPutAll: each ]
>      separatedBy: [ stream space ] ]
>
> Why should code like this be duplicated throughout the system? If the
> requirement is that join: is only to join strings (which is fine with me)
> then convert the input to strings! It's simple, see:
>
> SequenceableCollection>>join: delimiter
>  "Join the elements of the receiver using the given delimiter"
>  ^String streamContents:[:s|
>    self do:[:each| s nextPutAll: each asString]
>         separatedBy:[s nextPutAll: delimiter asString]].
>
> and the first example becomes:
>
> ClassDescription>>instanceVariablesString
>  "Answer a string of my instance variable names separated by spaces."
>  ^self instVarNames join: ' '
>
> This is a muchly improved version as far as I am concerned.
>
>> This is similar. I'd say the best way to improve #sum would be to delete
>> it.
>
> It is indeed similar. In such that Collection>>sum is just as useful a
> utility that should be supported as well. I see no problem in requiring that
> #sum is only valid for non-empty input and the result is undefined
> (returning, nil, 0, or an error) if used on an empty collection.
>
> Cheers,
>  - Andreas