From: matz@... Date: 2021-05-21T07:07:03+00:00 Subject: [ruby-core:103939] [Ruby master Bug#17631] `Numeric#real?` incorrectly returns true for `NaN` and `INFINITY` Issue #17631 has been updated by matz (Yukihiro Matsumoto). Status changed from Open to Rejected Traditionally, `real` just means being floating-point numbers in Computer Science. Other languages treat infinity and `NaN` in similar manner. Matz. ---------------------------------------- Bug #17631: `Numeric#real?` incorrectly returns true for `NaN` and `INFINITY` https://bugs.ruby-lang.org/issues/17631#change-92069 * Author: jtannas (Joel Tannas) * Status: Rejected * Priority: Normal * ruby -v: ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-linux] * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN ---------------------------------------- In mathematics, infinity is not a real number. See https://math.stackexchange.com/a/750787 I don't have a source for this, but I also believe that `NaN` is not a real number. `Numeric#real?` incorrectly returns `true` for both of these cases. ``` ruby irb(main):001:0> Float::INFINITY.real? => true irb(main):002:0> Float::NAN.real? => true irb(main):003:0> require 'bigdecimal' => true irb(main):004:0> BigDecimal::NAN.real? => true irb(main):005:0> BigDecimal::INFINITY.real? => true ``` I ran into this while doing some math with logarithms, leading me to have to put in weird catches like `return nil if result.complex? || result.nan? || result.infinite?` --- Originally reported here: https://stackoverflow.com/q/64795265/7950458 -- https://bugs.ruby-lang.org/ Unsubscribe: