13.1. If ‘[p f a]’ is in K′, we will say that ‘p’ is a value of ‘f’ at ‘a’.

13.2. If ‘a’ and ‘b’ are rational U-reals and if ‘b’ is not less than ‘a’, then ‘{a, b}’ will be called a rational U-interval.

13.3. If ‘f’ has a value at ‘d’, if ‘d’ is within a U-interval ‘{c, e}’, and if all values of ‘f’ at U-reals with ‘{c, e}’ are within the U-interval ‘{r, t}’, then we will say that ‘{c, e}’ restricts ‘f’ to ‘{r, t}’ at ‘d’, and that ‘{c, e}’ is an ‘f’-restrictive correlate of ‘d’ with respect to ‘{r, t}’.

13.4. If ‘d’ is within ‘{a, b}’, we will say that ‘{a, b}’ “contains” ‘d’.

13.5. If ‘f’ has a value at ‘d’ and if corresponding to every U-interval ‘{r, t}’ that contains a value of ‘f’ at ‘d’ there is an ‘f’-restrictive correlate of ‘d’ with respect to ‘{r, t}’, then ‘f’ will be said to be “continuous” at ‘d’. Without loss of generality the ‘f’-restrictive correlate can be required to be a rational U-interval.

13.6. If ‘f’ is continuous at every U-real in ‘{a, b}’, we will say that ‘f’ is continuous in ‘{a, b}’.

13.7. Theorem. If ‘k’ is a positive U-real and ‘f’ is continuous in a U-interval ‘{a, b}’, then ‘{a, b}’ is covered by the class S of rational U-intervals that are ‘f’-restrictive correlates of rational U-reals in ‘{a, b}’ with respect to those rational U-intervals ‘{r, t)’ that contain values of ‘f’ at rational U-reals in ‘{a, b}’ and that are such that’∣t − r∣‘ is equal to ‘k’ (in the sense of 10.10).