strange behaviour when comparing floating points in rspec

Question

the 3rd of the following tests fails:

  specify { (0.6*2).should eql(1.2) }
  specify { (0.3*3).should eql(0.3*3) }
  specify { (0.3*3).should eql(0.9) } # this one fails

Why is that? Is this a floating point issue or a ruby or rspec issue?

Answer 1

As of rspec-2.1

specify { (0.6*2).should be_within(0.01).of(1.2) }

Before that:

specify { (0.6*2).should be_close(1.2, 0.01) }