Manually applied Jens Axel's patch to add `random-prime'

collects/math/private/number-theory/number-theory.rkt

@@ -12,6 +12,7 @@
          
          ; primes
          nth-prime
+         random-prime
          next-prime untyped-next-prime
          next-primes
          prev-prime untyped-prev-prime
@@ -286,6 +287,14 @@
          (for/fold: ([p : Prime  2]) ([m (in-range n)])
            (next-prime p))]))
 
+(: random-prime : Z -> Prime)
+(define (random-prime n)
+  (when (<= n 2)
+    (raise-argument-error 'random-prime "Natural > 2" n))
+  (define p (random-natural n))
+  (if (prime? p)
+      p
+      (random-prime n)))
 
 ;;;
 ;;; FACTORIZATION

collects/math/scribblings/math-number-theory.scrbl

@@ -304,6 +304,18 @@ Returns the @racket[n]th positive prime; @racket[n] must be nonnegative.
                     (nth-prime 2)]
 }
 
+@defproc[(random-prime [n Integer]) Natural]{
+Returns a random prime smaller than @racket[n], which must be greater than @racket[2].
+                                    
+The function @racket[random-prime] picks random numbers
+below @racket[n] until a prime is found.
+
+@interaction[#:eval untyped-eval
+                    (random-prime 10)
+                    (random-prime 10)
+                    (random-prime 10)]
+}
+
 @defproc[(next-prime [z Integer]) Integer]{
 Returns the first prime larger than @racket[z].