NATP.html -- ACL2 Version 6.3

### NATP

a recognizer for the natural numbers

    Major Section:  ACL2-BUILT-INS

The natural numbers is the set of all non-negative integers, `{0,1,2,3,...}`. `Natp` returns `t` if and only its argument is a natural number, and `nil` otherwise. We recommend the community book `books/arithmetic/natp-posp.lisp` as a book for reasoning about `posp` and `natp`. This book is included by community books `books/arithmetic/top` and `books/arithmetic/top-with-meta`.

To see the ACL2 definition of this function, see pf.