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Encyclopedia > Pairing function

In mathematics a pairing function is a process to uniquely encode two natural numbers into a single natural number.


Pairing functions are used in set theory to prove that integers and rational numbers have the same cardinality as natural numbers. In theoretical computer science they are used to encode a function defined on a vector of natural numbers f:NkN into a new function g:NN.


Definition

A pairing function is a bijective function

External link


  Results from FactBites:
 
Computable function - Wikipedia, the free encyclopedia (1960 words)
If a computable function is defined then it returns a single natural number as output (this output can be interpreted as a list of numbers using a pairing function).
The fact that these models give equivalent classes of computable functions stems from the fact that each model is capable of reading and mimicking a procedure for any of the other models, much as a compiler is able to read instructions in one computer language and emit instructions in another language.
The notion of computability of a function can be relativized to an arbitrary set of natural numbers A, or equivalently to an arbitrary function f from the naturals to the naturals, by using Turing machines (or any other model of computation) extended by an oracle for A or f.
PlanetMath: alternative characterizations of recursive functions (348 words)
The class of recursive functions may be characterized by considerably weaker conditions than those given in the entry “recursive function” of this encyclopaedia.
By means of a pairing function, the definition may be simplified considerably.
This is version 8 of alternative characterizations of recursive functions, born on 2004-09-04, modified 2006-10-08.
  More results at FactBites »


 

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