• kogasa@programming.dev
      ·
      1 year ago

      Computable. There are countably many computable numbers since there are only countably many possible programs. Non-computable numbers can't be exactly referred to / described / constructed by a program, so if your point of view is that everything is a program, you would say they don't exist.

      • silent_water [she/her]
        ·
        1 year ago

        homotopy type theory has a way to describe the reals in full generality via cauchy sequences, so if type checking ever gets proven to be decidable, this won't be true any longer. it's chapter 11 in the hott book.

        • kogasa@programming.dev
          ·
          1 year ago

          I guarantee you're misunderstanding or accidentally misrepresenting something here. The fact that there are only countably many computable numbers is a simple consequence of the fact that there are only countably many programs, which is bounded above by the number of finite sequences of letters from a finite alphabet, which is countably infinite.

          There may be more finitistic/computable models for the real numbers or something, but "the computable real numbers" are countable.

          • silent_water [she/her]
            ·
            1 year ago

            the model provided is a lazy cauchy sequence so any given real number can be computed to arbitrary precision. the theorems about real numbers are directly provable and potentially machine checkable, assuming decidable type checking works out.

            • kogasa@programming.dev
              ·
              1 year ago

              Nothing about what you said contradicts what I said. You can either change the definition of the computable real numbers, or agree that they are countable.

      • dat_math [they/them]
        ·
        1 year ago

        The meme is about computability of numbers though, not countability of sets of them