Issue #12217 has been updated by Akira Tanaka.


Akira Tanaka wrote:
> - Enumerable#sum is not well defined for non-numeric elements, especially objects without + method.

An idea to avoid this problem is an argument to specify the initial object.

```
module Enumerable
  def sum(init=0)
    inject(init, :+) # or better algorithm.
  end
end
```

Programmers have responsibility that init has + method.

However init has the default value 0 because #sum is mostly used for numeric.


----------------------------------------
Feature #12217: Introducing Enumerable#sum for precision compensated summation and revert r54237
https://bugs.ruby-lang.org/issues/12217#change-57702

* Author: Kenta Murata
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
----------------------------------------
In this issue I propose to introduce Enumerable#sum for precision compensated summation of an array of floating point numbers.

In r54237, I've changed Enumerable#inject to support precision compensated summation for summing up floating point numbers.
But I noticed that this commit broke the equality of `ary.inject(:+) == ary.inject {|a, x| a + x }`.
I think this equality is important property of inject method, so I don't want to break it.

And because precision compensated algorithms are complicated, I think they are provided in the standard library, especially simple summation.


---Files--------------------------------
inject-plus.txt (1.21 MB)


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