Is there a computable function $F: \mathbb N_0^2 \rightarrow \mathbb N_0$, such that for every computable function $f: \mathbb N_0 \rightarrow \mathbb N_0$, there exists an $e \in \mathbb N_0$, such that $F(e, x) = f(x), \forall x \in \mathbb N_0.$

My intuition says there is not, but I haven't found a formal proof. Can anyone confirm my suspicions or know a proof?


1 Answer 1


Yes there is. Such an $F$ is called a universal Turing machine.

$e$ is then just an encoding of the Turing machine that computes $f$.


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