Gödel Numbering

January 16, 2015

Gödel numbering is a system that assigns a natural number to each symbol and expression in a logical system, invented in 1931 by Kurt Gödel for the proofs of his incompleteness theorems. Consider the logical system where symbols are letters and expressions are words; for instance, the word PRAXIS consists of six symbols P, R, A, X, I, and S. Gödel numbering would assign numbers to the letters, say A=1 … Z=26, then assign each letter as the exponent of the next prime, so PRAXIS would be numbered 216 × 318 × 51 × 724 × 119 × 1319 =


The process is reversible; factor the Gödel number and decode the exponents.

Your task is to write functions that encode strings as Gödel numbers and decode Gödel numbers as strings. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.


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