From: Kornelius Kalnbach <murphy@...>
Date: 2009-11-01T22:56:14+09:00
Subject: [ruby-core:26471] Re: New Features for the Array Module

Daniel Cohen wrote:
> A sum function, that sums the elements in an array if they are
> numbers;
I use this one a lot; I actually thought it was in 1.9 already!

The ActiveSupport implementation of Array#sum is particularly useful
because #+ is defined for a lot of classes, like Strings (so #sum works
like #join) or Arrays (a one-level #flatten).

Your patch limits the method to Floats; this is not Ruby-like, in my
view, even if it is faster.

> and a mean (or average) function that finds the mean of the
> elements in the the array using the sum function.
This one, however, really only applies to numerical objects. I'm not
sure about such a method being included into standard Ruby, especially
when it can be added with

  class Array
    def mean
      sum / size
    end
  end

easily.

So:
+1 for Array#sum if it is defined as #inject(&:+)
-1 on type-limited Array#sum and Array#mean

On second thought: Why not implement this as Enumerable#sum?

[murphy]