[ruby-core:102816] [Ruby master Bug#6120] Float and BigDecimal bug in remainder in corner cases

Issue #6120 has been updated by jeremyevans0 (Jeremy Evans).


I've submitted a pull request to fix this issue for Integer/Float: https://github.com/ruby/ruby/pull/4257

I've submitted an issue to the bigdecimal repository to fix the issue in BigDecimal: https://github.com/ruby/bigdecimal/issues/187

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Bug #6120: Float and BigDecimal bug in remainder in corner cases
https://bugs.ruby-lang.org/issues/6120#change-90870

* Author: marcandre (Marc-Andre Lafortune)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
* ruby -v: r34927
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
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Currently:

    4.2.remainder(+Float::INFINITY) # => 4.2, ok
    4.2.remainder(-Float::INFINITY) # => NaN, should be 4.2
    # (same with all signs reversed)

Reasons the remainder should be 4.2 and not NaN:
1) foo.remainder(bar) == foo.remainder(-bar)
2) foo.remainder(bar) == foo  when bar.abs > foo.abs

Similarly:
    require 'bigdecimal'
    bd = BigDecimal.new("4.2")
    bd.remainder(BigDecimal.new("+Infinity"))  # => NaN, should be bd
    bd.remainder(BigDecimal.new("-Infinity"))  # => NaN, should be bd
    # (same with all signs reverse)

Reasons: same as float.

Finally:
    bd = BigDecimal.new("4.2")
    bd.modulo(BigDecimal.new("0"))  # => ZeroDivisionError, probably ok?
    bd.remainder(BigDecimal.new("0"))  # => NaN, should be probably raise a ZeroDivisionError?

Like in #6044, this could be decided either way, as long as there is consistency. Anyone prefer NaN to raising a ZeroDivisionError?




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