(scheme base) member: return #f, not (), for no match

* module/scheme/base.scm (member): Match the r7rs requirement, as assoc
  already does.

Thanks to Erik Dominikus for reporting the problem.

Closes: 43304

THANKS

@@ -2,6 +2,7 @@ Contributors since the last release:
 
     Christopher Baines
            Greg Benison
+	    Rob Browning
         Tristan Colgate-McFarlane
           Aleix Conchillo Flaqué
         Ludovic Courtès
@@ -79,6 +80,7 @@ For fixes or providing information which led to a fix:
            Josh Datko
           David Diffenbaugh
           Hyper Division
+           Erik Dominikus
       Alexandre Duret-Lutz
            Nils Durner
          John W Eaton

module/scheme/base.scm

@@ -129,9 +129,10 @@
     (unless (procedure? =)
       (error "not a procedure" =))
     (let lp ((ls ls))
-      (if (or (null? ls) (= (car ls) x))
-          ls
-          (lp (cdr ls)))))))
+      (cond
+       ((null? ls) #f)
+       ((= (car ls) x) ls)
+       (else (lp (cdr ls))))))))
 
 (define* (assoc x ls #:optional (= equal?))
   (cond

test-suite/tests/r7rs.test

@@ -2171,7 +2171,7 @@
        (let ((out (open-output-string))
              (x (list 1)))
          (set-cdr! x x)
-         (write x out)
+         (write-shared x out)
          (get-output-string out))
        ;; labels not guaranteed to be 0 indexed, spacing may differ
        '("#0=(1 . #0#)" "#1=(1 . #1#)"))