We can get faster fib just returning two values

How do you make fib fast?
I don't recomend using memoization because it require waste memory.
I recommend returning two values.

RSpec and Cucumber

I'm reading The RSpec Book.

I've understand:

• RSpec should be used to describe the behavior of objects.
• For describing the behavior of a library, Cucumber should be used.

Free online textbooks for computer arithmetic

I'm the maintainer of the bigdecimal library of CRuby.  Recently, I'm studying computer arithmetic so improving the performance of the bigdecimal.  My favorite text is TAOCP vol. 2.

Today, I found two free online textbooks for computer arithmetic.  Although I've read just their preface parts, I'm believing it is bliss that they are available as free media.

• R. P. Brent and P. Zimmermann. Modern Computer Arithmetic (version 0.5.1). arXiv:1004.4710 (27 Apr 2010)
• R. P. Brent. The complexity of multiple-precision arithmetic. arXiv:1004.3608 (2010)

Would you please tell me another text books if anyone know them.