The author claims that this set is countable but not sure if that is true. My argument is based on Cantor's theorem [1], which states that the power set has car

The author claims that this set is countable but not sure if that is true. My argument is based on Cantor's theorem [1], which states that the power set has cardinality strictly greater than the set. In order for the set of symbols to be finite field it must grow therefore since rational is infinitely countable from Cantor it must hold that "useful reals" is uncountable. [1] https://en.wikipedia.org/wiki/Cantor%27s_theorem https://en.wikipedia.org/wiki/Cantor%27s_theorem