[kbrkbr]

> Literally any definition of something infinite can always be reduced to a procedure that recursively transforms or observes some prior state.

Could you come up with or point to such a procedure for R (the reals)?

As I understand the diagonalization argument you can do that for N, but not for R.

[ludston]

Yes? Take any natural or real number. If it has no decimal point add one. Then append any digit. Repeat as necessary.

[falserum]

1, 1.1, 1.01, 1.001, …

This will never reach 2, so it will not generate all real numbers. (Which was what parent was asking for, to recusively generate all R)

[ludston]

You can define a procedure that reaches 2 very trivially. e.g. you generate all possible 1 digit numbers, then 2 digit numbers, then 3 digit numbers, etc.

This is how natural numbers work in the first place. You're just adding a decimal point to all of the possible places it could go.

[falserum]

Thanks for reply.

When will this reach PI or e or sqrt(2)?

(There are infinitely many numbers that will not be reached by this procedure)

[ludston]

Well, you have to ask yourself what is PI really? You've been taught it is a number with infinite decimal places, however, practically speaking when you use PI you actually round. Practically speaking this doesn't matter because it's not actually possible to have a shape with infinite points in reality so you only need to approximate to whatever fidelity suits you.

How is this? This is because PI is not actually a number. It's a procedure that generates digits for approximating things about circles.

This is the same with sqrt(2). The sqrt procedure emits digits just as the procedure to find all real numbers does.

You can't "reach" PI for the same reason that a natural number can't reach "f(x) => x + 1". That is, natural numbers aren't procedures or functions.

[falserum]

Fun.

What about 1/3, 1/7, …? Previously outlines recursive procedure doesn’t generate those.

But yeah, if you deny existance of irrational numbers, and redefine Real:=Rational, then you can generate these “real” numbers recursively and it does follow that all infinities have same cardinality here.

Btw. what is the diagonal of a unit square formed by 4 objects at the corners? I assume it is a rational number. Btw2. If you take that answer and multiply by itself, what do you get?

[kbrkbr]

If you could, you could use that procedure to create a mapping

1 => first step in the procedure 2 => second step ...

That in turn would mean that N and R have the same cardinality. This would be news.

[ludston]

If infinities don't exist then R and N don't have cardinality so that's not really a problem.

[kbrkbr]

It seems to me that this comes at the price that now in your geometry the diagonal of a unit square does not have a defined length. Only an approximate one of 1.41421, but what does this approximate?