From: Run Paint Run Run <redmine@...>
Date: 2009-07-01T04:39:40+09:00
Subject: [ruby-core:24099] [Bug #1708] require 'complex' Causes Unexpected Behaviour

Bug #1708: require 'complex' Causes Unexpected Behaviour
http://redmine.ruby-lang.org/issues/show/1708

Author: Run Paint Run Run
Status: Open, Priority: Normal
Category: lib
ruby -v: ruby 1.9.2dev (2009-06-27 trunk 23871) [i686-linux]

1.9 has Complex in core, yet on 1.8 you had to explicitly require it with "require 'complex'". However, 1.9 also has a 'complex.rb' in its lib directory which in turn requires 'cmath.rb'. 'cmath.rb' redefines quite a few Math methods. This is particularly confusing because you would expect "require 'complex'" to be a no-op on 1.9, whereas it actually causes Math methods to fail in mysterious ways.

For example, where Math used to raise TypeErrors it now raises NoMethodErrors. This happens for all of the overridden methods.

    >> Math.atan(nil)
    TypeError: can't convert nil into Float
	from (irb):1:in `atan'
	from (irb):1
	from /usr/local/bin/irb:12:in `<main>'
    >> require 'complex'
    => true
    >> Math.atan(nil)
    NoMethodError: undefined method `real?' for nil:NilClass
	from /usr/local/lib/ruby/1.9.1/cmath.rb:145:in `atan'
	from (irb):3
	from /usr/local/bin/irb:12:in `<main>'

As Complex is in core Math methods should work with complex numbers by default. This half-in-, half-out-, approach is confusing. If the current behavior is intentional, it needs to be clarified in the Math and Complex documentation.


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