Move remf from unstable/list to racket/list.

Add remf* for consistency.

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

@@ -1312,6 +1312,32 @@ Computes the n-ary cartesian product of the given lists.
 ]
 }
 
+@defproc[(remf [pred procedure?]
+               [lst list?])
+         list?]{
+Returns a list that is like @racket[lst], omitting the first element of @racket[lst]
+for which @racket[pred] produces a true value.
+
+@defexamples[
+#:eval list-eval
+(remf negative? '(1 -2 3 4 -5))
+]
+
+}
+
+@defproc[(remf* [pred procedure?]
+                [lst list?])
+         list?]{
+Like @racket[remf], but removes all the elements for which @racket[pred]
+produces a true value.
+
+@defexamples[
+#:eval list-eval
+(remf* negative? '(1 -2 3 4 -5))
+]
+
+}
+
 
 @close-eval[list-eval]
 

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

@@ -616,4 +616,15 @@
 (test '((1 2) (3 4) (4 3)) split*-list '(1 2 3 4) '(1 2 4 3) =)
 (err/rt-test (split*-list '() '() #f))
 
+;; ---------- remf / remf* ----------
+
+(test '() remf positive? '())
+(test '(-2 3 4 -5) remf positive? '(1 -2 3 4 -5))
+(test '(1 3 4 -5) remf even? '(1 -2 3 4 -5))
+(test '(1 -2 3 4 -5) remf (λ (x) #f) '(1 -2 3 4 -5))
+(test '() remf* positive? '())
+(test '(-2 -5) remf* positive? '(1 -2 3 4 -5))
+(test '(1 3 -5) remf* even? '(1 -2 3 4 -5))
+(test '(1 -2 3 4 -5) remf* (λ (x) #f) '(1 -2 3 4 -5))
+
 (report-errs)

racket/collects/racket/list.rkt

@@ -50,7 +50,9 @@
          argmin
          argmax
          group-by
-         cartesian-product)
+         cartesian-product
+         remf
+         remf*)
 
 (define (first x)
   (if (and (pair? x) (list? x))
@@ -747,3 +749,27 @@
   (define (cp-2 as bs)
     (for*/list ([i (in-list as)] [j (in-list bs)]) (cons i j)))
   (foldr cp-2 (list (list)) ls))
+
+(define (remf f ls)
+  (unless (list? ls)
+    (raise-argument-error 'remf "list?" ls))
+  (unless (and (procedure? f)
+               (procedure-arity-includes? f 1))
+    (raise-argument-error 'remf "(-> any/c any/c)" f))
+  (cond [(null? ls) '()]
+        [(f (car ls)) (cdr ls)]
+        [else
+         (cons (car ls)
+               (remf f (cdr ls)))]))
+
+(define (remf* f ls)
+  (unless (list? ls)
+    (raise-argument-error 'remf* "list?" ls))
+  (unless (and (procedure? f)
+               (procedure-arity-includes? f 1))
+    (raise-argument-error 'remf* "(-> any/c any/c)" f))
+  (cond [(null? ls) '()]
+        [(f (car ls)) (remf* f (cdr ls))]
+        [else
+         (cons (car ls)
+               (remf* f (cdr ls)))]))