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From: chris@chrisseaton.com
To: ruby-core@ruby-lang.org
Subject: [ruby-core:99434] [Ruby master Bug#17098] Float#negative? reports negative zero as not negative
Date: Sat, 01 Aug 2020 12:50:48 +0000 (UTC)
Message-ID: <redmine.journal-86887.20200801125048.8671@ruby-lang.org> (raw)
In-Reply-To: <redmine.issue-17098.20200801010523.8671@ruby-lang.org>

Issue #17098 has been updated by chrisseaton (Chris Seaton).


My suggestion is that `Float#negative?(neg_zero) == true` and `Float#positive?(pos_zero) == false`.

We can't get rid of negative zero - it's a standard part of floating point numbers as implemented by the hardware. It's also useful in some applications.

----------------------------------------
Bug #17098: Float#negative? reports negative zero as not negative
https://bugs.ruby-lang.org/issues/17098#change-86887

* Author: chrisseaton (Chris Seaton)
* Status: Open
* Priority: Normal
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
Is this intended behaviour?

```
irb(main):001:0> neg_zero = -0.0
=> -0.0
irb(main):002:0> neg_zero.negative?
=> false
irb(main):003:0> neg_zero < 0
=> false
```

It happens because `Numeric#negative?` uses `< 0`. My understanding of IEEE floating point is that negative zero is not less than zero, but I think it should still report as negative.



-- 
https://bugs.ruby-lang.org/

  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01  1:05 [ruby-core:99426] " chris
2020-08-01  2:18 ` [ruby-core:99427] " merch-redmine
2020-08-01 12:18 ` [ruby-core:99432] " chris
2020-08-01 12:38 ` [ruby-core:99433] " sawadatsuyoshi
2020-08-01 12:50 ` chris [this message]
2020-08-01 16:00 ` [ruby-core:99441] " chris
2020-08-01 18:02 ` [ruby-core:99442] " eregontp
2020-08-01 19:41 ` [ruby-core:99443] " marcandre-ruby-core
2020-08-02 12:21 ` [ruby-core:99444] " sawadatsuyoshi

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