[ruby-core:74569] [Ruby trunk Feature#12217] Introducing Enumerable#sum for precision compensated summation and revert r54237

From: muraken@...
Date: 2016-03-25 11:41:40 UTC
List: ruby-core #74569
Issue #12217 has been reported by Kenta Murata.

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

* Author: Kenta Murata
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
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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.




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