How to show that integer subtraction is primitive recursive function?

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- Dec 2nd 2010, 03:31 AMApprentice123Primitive Recursive Function
How to show that integer subtraction is primitive recursive function?

- Dec 2nd 2010, 11:24 AMSoroban
Hello, Apprentice123!

To make it easier (for me), I'll consider positive integers only.

Quote:

Show that integer subtraction is primitive recursive function.

Consider the subtraction: .$\displaystyle a - b$

Let $\displaystyle a_0 = a$

Then: .$\displaystyle a_n \:=\:a_{n-1} - 1\;\text{ for }n = 1,2,3,\hdots\:b.$

. . The answer is: .$\displaystyle a_b$