ZEROP.html -- ACL2 Version 6.3

### ZEROP

test an acl2-number against 0

    Major Section:  ACL2-BUILT-INS

`(zerop x)` is `t` if `x` is `0` and is `nil` otherwise. Thus, it is logically equivalent to `(equal x 0)`.

`(Zerop x)` has a guard requiring `x` to be numeric and can be expected to execute more efficiently than `(equal x 0)` in properly guarded compiled code.

In recursions down the natural numbers, `(zp x)` is preferred over `(zerop x)` because the former coerces `x` to a natural and allows the termination proof. In recursions through the integers, `(zip x)` is preferred. See zero-test-idioms.

`Zerop` is a Common Lisp function. See any Common Lisp documentation for more information.

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