Real number

I am not yet sure how to define real numbers. Many irrational numbers (e.g. ${\sqrt {2}}$ and $\pi$) are in fact real, but the standard definition of the reals involves infinite nonsense.

Examples

Any fraction.

Any algebraic number like ${\sqrt {2}}$.

Pi

e

The output of the following computer program

digit(int i): if

 
digit(int i): 
if (suthaweou) 
return 0