Can We Enumerate All Primitive Recursive Functions?

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Discussion Overview

The discussion centers on the enumeration of primitive recursive functions, exploring whether it is possible to list all such functions and its implications, particularly in relation to Ackermann's function and its classification as non-primitive recursive.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions if enumerating primitive recursive functions can demonstrate that Ackermann's function is not primitive recursive.
  • Another participant suggests that the proof regarding Ackermann's function involves proving something for all primitive recursive functions by enumerating all possible derivations.
  • A further inquiry seeks clarification on whether "enumerating all possible derivations" refers to listing all definitions of primitive recursive functions, including basic functions and those defined by composition or recursion.
  • One participant affirms the understanding of enumeration as encompassing all possible cases of how primitive recursive functions are defined.

Areas of Agreement / Disagreement

Participants express differing views on the implications of enumeration for Ackermann's function, and the discussion remains unresolved regarding the relationship between enumeration and the classification of functions.

Contextual Notes

Limitations include potential ambiguities in definitions of primitive recursive functions and the scope of enumeration methods discussed.

mathmari
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Hey! :o

Can we enumerate the primitive recursive functions?
 
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Of course, just enumerate all possible derivations (definitions).
 
Is the enumeration of primitve recursive functions an other way to show that Ackermann's function is not primitive recursive? Or isn't it possible?
 
In the proof that Ackermann's function is not p.r. you prove something for all p.r. functions, and you do this by enumerating all possible derivations.
 
Evgeny.Makarov said:
In the proof that Ackermann's function is not p.r. you prove something for all p.r. functions, and you do this by enumerating all possible derivations.

By "enumerating all possible derivations" do you mean that we enumerate all possible cases how the p.r. function is defined, if it is one of the basic functions (constant, successor, projection), or is defined by compositions or primitive recursions?
 
Yes.
 

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