From: stan001212@...
Date: 2020-01-22T08:42:52+00:00
Subject: [ruby-core:96966] [Ruby master Bug#16518] Should we rationalize Rational's numerator automatically?

Issue #16518 has been updated by st0012 (Stan Lo).


Thanks for the quick response!

I also found that it returns `BigDecimal` if any of its arguments is a `BigDecimal`:

```
irb(main):005:0> Rational(BigDecimal(1), 1).class
=> BigDecimal
irb(main):006:0> Rational(BigDecimal(1), BigDecimal(1)).class
=> BigDecimal
irb(main):007:0> Rational(0, BigDecimal(1)).class
=> BigDecimal
irb(main):008:0>
```

----------------------------------------
Bug #16518: Should we rationalize Rational's numerator automatically?
https://bugs.ruby-lang.org/issues/16518#change-83991

* Author: st0012 (Stan Lo)
* Status: Open
* Priority: Normal
* Assignee: mrkn (Kenta Murata)
* Target version: 
* ruby -v: 2.6.5
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
In this [Rails issue](https://github.com/rails/rails/issues/38041) we found that using `BigDecimal` as a `Rational`'s numerator can have inconsistent behaviors when the denominator gets bigger. For example:

```
> 1 == BigDecimal(1)
=> true
> Rational(1, 1) == Rational(BigDecimal(1), 1)
=> true
> Rational(1, 6) == Rational(BigDecimal(1), 6)
=> true
> Rational(1, 60) == Rational(BigDecimal(1), 60)
=> false
```


So my question is, is this behavior expected? 
If it's not expected, do we have a plan to fix it?
If it is, does it make sense to manually rationalize the numerator before passing it into the `Rational` call, in order to get a consistent result?



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