sum: should work with empty collection

[Ducasse]

#() sum: #linesOfCode should return 0.

right now it forces all the clients to check if the receiver is empty.
If we do not fix it, we should remove it and the user uses inject:into:

[Ducasse]

So just adding a self isEmpty ifTrue: [^ 0 ] would make it a lot more usable

[svenvc]

Here we go again ...

(And it totally agree: https://en.wikipedia.org/wiki/Empty_sum)

Empty sum - Wikipedia

[Ducasse]

thanks!
And we will fix it or remove it.
We can add sumNumbers: to help :)

[VincentBlondeau]

What about adding sum:ifEmpty:?

#() sum: #linesOfCode ifEmpty: [0]

[bencoman]

I find that Wikipedia article hard to follow. I think this is a simpler explanation in favour...
https://math.stackexchange.com/a/2310799

Mathematics Stack Exchange

Empty set and empty sum

Empty set is closed under addition. If not, there would be at least one element in the empty set whose addition with itself is not there, contradiction. Thus the result follows. This not a conventi...

[Ducasse]

Yes vincent I like your idea!
I think that it solves many problem.

[olekscode]

This issue should be closed because the PR #6453 has been merged and the duplicated issue #6452 has been closed