From: shibata.hiroshi@... Date: 2014-08-27T02:45:02+00:00 Subject: [ruby-core:64568] [ruby-trunk - Bug #2121] [Closed] mathn/rational destroys Fixnum#/, Fixnum#quo and Bignum#/, Bignum#quo Issue #2121 has been updated by Hiroshi SHIBATA. Status changed from Assigned to Closed mathn library is deprecated on trunk [Feature #10169] ---------------------------------------- Bug #2121: mathn/rational destroys Fixnum#/, Fixnum#quo and Bignum#/, Bignum#quo https://bugs.ruby-lang.org/issues/2121#change-48497 * Author: Charles Nutter * Status: Closed * Priority: Normal * Assignee: Keiju Ishitsuka * Category: lib * Target version: * ruby -v: Any 1.8.6 or higher * Backport: ---------------------------------------- =begin I've known this for a while, but only now realized this is actually a terrible bug. The mathn library replaces Fixnum#/ and Bignum#/ causing them to return a different value. When the result of a division is not an integral value, the default versions will return 0. I can think of many algorithms that would use this expectation, and most other languages will not upconvert integral numeric types to floating-point or fractional types without explicit consent by the programmer. When requiring 'mathn', Fixnum#/ and Bignum#/ are replaced with versions that return a fractional value ('quo') causing a core math operator to return not just a different type, but *a different value*. No core library should be allowed to modify the return value of core numeric operators, or else those operators are worthless; you can't rely on them to return a specific value *ever* since someone else could require 'mathn' or 'rational'. Note also that 'rational' destroys Fixnum#quo and Bignum#quo. This is also a bug that should be fixed, though it is less dangerous because they're not commonly-used operators. The following code should not fail; Fixnum#/ should never return a value of a different magnitude based on which libraries are loaded: {{{ require 'test/unit' class TestFixnumMath < Test::Unit::TestCase # 0 to ensure it runs first, for illustration purposes def test_0_without_mathn assert_equal 0, 1/3 end def test_with_mathn require 'mathn' assert_equal 0, 1/3 end end }}} But it does fail: {{{ ~/projects/jruby ��� ruby test_fixnum_math.rb Loaded suite test_fixnum_math Started .F Finished in 0.016003 seconds. 1) Failure: test_with_mathn(TestFixnumMath) [test_fixnum_math.rb:11]: <0> expected but was <1/3>. 2 tests, 2 assertions, 1 failures, 0 errors }}} =end -- https://bugs.ruby-lang.org/