From: duerst@...
Date: 2020-05-10T00:34:39+00:00
Subject: [ruby-core:98245] [Ruby master Bug#16843] A bug with floating point	multiplication

Issue #16843 has been updated by duerst (Martin D�rst).


Just as an add-on:
Go has similar effects to those reported here for Ruby, see e.g. https://stackoverflow.com/questions/33640943/golang-float-arithmetic.
@FedorKK, if you can find out *why* e.g. `fmt.Println(0.29 * 100 == 29.0)` prints true in Go, please tell us.

----------------------------------------
Bug #16843: A bug with floating point multiplication
https://bugs.ruby-lang.org/issues/16843#change-85486

* Author: FedorKK (Fedor Koshel)
* Status: Rejected
* Priority: Normal
* ruby -v: 2.6.6, 2.7.1
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
I've reproduced it with both currently stable versions: 2.6.6 and 2.7.1.

``` ruby
irb(main):001:0> 0.29 * 100
=> 28.999999999999996
irb(main):002:0> 0.29 * 100.0
=> 28.999999999999996
irb(main):003:0> 0.28 * 100
=> 28.000000000000004
irb(main):004:0> 0.28 * 100.0
=> 28.000000000000004
irb(main):005:0> 0.27 * 100.0
=> 27.0
irb(main):006:0> 0.27 * 100
=> 27.0

$ ruby -v                                                                                                                                                                                                 
ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-linux]
```

``` ruby
irb(main):001:0> 0.29 * 100
=> 28.999999999999996
irb(main):002:0> 0.29 * 100.0
=> 28.999999999999996
irb(main):003:0> 0.28 * 100.0
=> 28.000000000000004
irb(main):004:0> 0.28 * 100
=> 28.000000000000004
irb(main):005:0> 0.27 * 100
=> 27.0
irb(main):006:0> 0.27 * 100.0
=> 27.0


$ ruby -v                                                                                                                                                                                                 
ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-linux]
```





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