[ruby-core:97571] [Ruby master Bug#16700] Inconsistent behavior of equal? between Integer and Float

Issue #16700 has been updated by Eregon (Benoit Daloze).


It's a side effect of MRI using C's `==` to implement `equal?`.

In TruffleRuby reference equality has its own logic, so the results are more consistent (e.g., all Floats are compared by their binary representation):
https://github.com/oracle/truffleruby/blob/74a40b57ffaafbc26fe1b9d3cf22cf21ad7191bf/src/main/java/org/truffleruby/core/basicobject/BasicObjectNodes.java#L89-L169

I guess MRI could do the same, but it would likely occur some performance hit.

In any case, comparing numbers by identity is usually an anti-pattern, and I think that's why MRI can be a bit loose on e.g. #equal? with Floats here.

----------------------------------------
Bug #16700: Inconsistent behavior of equal? between Integer and Float
https://bugs.ruby-lang.org/issues/16700#change-84724

* Author: thyresias (Thierry Lambert)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 2.6.5p114 (2019-10-01 revision 67812) [i386-mingw32]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
~~~ruby
0.equal?(0)  #=> true
0.0.equal?(0.0)  #=>  false
x = 0.0
x.equal?(x)  #=> true
~~~
Since Float objects are immutable, I would expect 0.0.equal?(0.0) to be true.



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