Add natural? as an alias for nonnegative-integer?

pkgs/racket-doc/scribblings/reference/numbers.scrbl

@@ -1298,6 +1298,9 @@ Returns @racket[#t] if @racket[x] is @racket[+inf.0], @racket[-inf.0], @racket[+
  Like @racket[exact-nonnegative-integer?], but also returns
  @racket[#t] for non-negative @racket[inexact?] integers.}
 
+@defproc[(natural? [x any/c]) boolean?]{
+ An alias for @racket[nonnegative-integer?].}
+
 @; ----------------------------------------------------------------------
 @close-eval[math-eval]
 @; ----------------------------------------------------------------------

pkgs/racket-test-core/tests/racket/math.rktl

@@ -174,6 +174,21 @@
 (test #f nonnegative-integer? 0.5)
 (test #f nonnegative-integer? -5)
 
+;; =========================================================================
+;; natural?
+
+(test #t natural? 1)
+(test #t natural? 1.0)
+(test #t natural? 3/3)
+(test #t natural? 0)
+(test #t natural? -0)
+(test #t natural? 0.0)
+(test #t natural? -0.0)
+(test #f natural? 3/2)
+(test #f natural? 0.5)
+(test #f natural? -5)
+
+
 ;; =========================================================================
 ;; sqr
 

racket/collects/racket/math.rkt

@@ -13,6 +13,7 @@
          negative-integer?
          nonpositive-integer?
          nonnegative-integer?
+         natural?
          sqr
          sgn conjugate
          sinh cosh tanh
@@ -46,6 +47,8 @@
   (define (nonnegative-integer? x)
     (and (integer? x) (not (negative? x))))
 
+  (define natural? nonnegative-integer?)
+
   ;; z^2
   (define (sqr z)
     (unless (number? z) (raise-argument-error 'sqr "number?" z))