Fortunately for us, mathematicians of the twentieth century realized this problem and proposed solutions. In order to focus on the essential problems at hand, we will deal only with natural numbers, and functions on natural numbers. This turns out to not be a serious restriction since natural numbers are robust enough to encode many objects (after all, our modern digital computers work with only zeros and ones).

— Computability Theory

— Joe Mileti

2013.12.25 Wednesday ACHK