Issue #12548 has been updated by Noah Gibbs.


Benoit Daloze says that RubySpec should test previous rounding behavior for Ruby before 2.4.0, and test round-even for 2.4.0+. That makes sense to me. Opened RubySpec PR #322 (https://github.com/ruby/spec/pull/322) to reflect this.

When/if we merge Nobu's branch for this bug, we should also ask RubySpec to merge PR #322 or something very similar.

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Bug #12548: Rounding modes inconsistency between round versus sprintf
https://bugs.ruby-lang.org/issues/12548#change-60971

* Author: Kieran McCusker
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 2.4.0
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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Hi

I've found this possible bug with sprintf in our production code, but it
seems very odd that no one has reported it so I'm doubting myself.

I've tested a few versions (CRuby 2.3.1 and 2.1.9) and it was present in
both.

To reproduce in irb:

sprintf('%1.0f', 12.5)

Expected result 13 actual 12

In fact if you look at the number sequence 0.5 -> 99.5 you find the even
half will all round down and the odd half round up. 12.5.round produces the correct result (13)

If you do the same in jruby 2.2.1 you get the expected result of 13.

Many thanks

Kieran


---Files--------------------------------
round_even.patch (4.43 KB)


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