This page contains automated test results for code from O'Reilly's Ruby Cookbook. If this code looks interesting or useful, you might want to buy the whole book.

Comparing Floating-Point Numbers
CodeExpectedActual
1.8 + 0.1
 1.9 1.9 
1.8 + 0.1 == 1.9
 false false 
1.8 + 0.1 > 1.9
 true true 
class Float
  def approx(other, relative_epsilon=Float::EPSILON, epsilon=Float::EPSILON)
    difference = other - self
    return true if difference.abs <= epsilon
    relative_error = (difference / (self > other ? self : other)).abs
    return relative_error <= relative_epsilon
  end
end
100.2.approx(100.1 + 0.1)
 true true 
10e10.approx(10e10+1e-5)
 true true 
100.0.approx(100+1e-5)
 false false 
printf("%.55f", 1.9)
 
1.8999999999999999111821580299874767661094665527343750000
 
1.8999999999999999111821580299874767661094665527343750000
 
printf("%.55f", 1.8 + 0.1)
 
1.9000000000000001332267629550187848508358001708984375000
 
1.9000000000000001332267629550187848508358001708984375000
 
Float::EPSILON
 2.22044604925031e-16 2.22044604925031e-16 
(1.8 + 0.1) - 1.9
 2.22044604925031e-16 2.22044604925031e-16 
class Float
  def absolute_approx(other, epsilon=Float::EPSILON)
    puts((other-self).abs)
    return (other-self).abs <= epsilon
  end
end
(1.8 + 0.1).absolute_approx(1.9)
 true true 
10e10.absolute_approx(10e10+1e-5)
 false false 
98.6.approx(98.66)
 false false 
98.6.approx(98.66, 0.001)
 true true