There are situations where #+ and #sum make sense but there is no additive identity. Here is an example: #((1 2 3) (4 5 6) (7 8 9)) sum
On Tue, 24 Mar 2020 at 02:46, James Foster <smallt...@jgfoster.net> wrote: > > > > On Mar 23, 2020, at 6:06 AM, Sven Van Caekenberghe <s...@stfx.eu> wrote: > > > > What you found out now is that the clever trick used to avoid picking an > > additive identity (picking an element, counting it twice and then > > subtracting it) leads to a loss of precision when floating point numbers > > are involved. This is an important issue. > > If this approach is to be preserved, then each class should have an additive > identity so instead of adding and subtracting an object, we let the object > tell us its zero. > > James
