diff --git a/list.rkt b/list.rkt
index 3966ff5..56ce6a6 100644
--- a/list.rkt
+++ b/list.rkt
@@ -1,5 +1,5 @@
 #lang racket/base
-(require racket/list)
+(require racket/list racket/set)
 (require "define.rkt" "len.rkt" "coerce.rkt")
 
 (define+provide/contract (trimf xs test-proc)
@@ -28,7 +28,7 @@
           (loop rest (cons item acc))))))
 
 
-(define+provide/contract (count-incidence x)
+(define+provide/contract (frequency-hash x)
   (list? . -> . hash?)
   (define counter (make-hash))
   (for ([item (flatten x)]) 
@@ -36,22 +36,26 @@
   counter)
 
 
+
+
+
 (define+provide/contract (members-unique? x)
-  (any/c . -> . boolean?)
+  ((or/c list? vector? string?) . -> . boolean?)  
   (cond 
-    [(list? x) (= (len (remove-duplicates x)) (len x))]
-    [(vector? x) (members-unique? (vector->list x))]
-    [(string? x) (members-unique? (string->list x))]
-    [else (error (format "members-unique cannot be determined for ~a" x))]))
+      [(list? x) (= (len (remove-duplicates x)) (len x))]
+      [(vector? x) (->list x)]
+      [(string? x) (string->list x)]
+      [else (error (format "members-unique? cannot be determined for ~a" x))]))
+
 
 
 (define+provide/contract (members-unique?/error x)
   (any/c . -> . boolean?)
   (define result (members-unique? x))
   (if (not result)
-      (let* ([duplicate-keys (filter-not empty? (hash-map (count-incidence x) 
+      (let* ([duplicate-keys (filter-not empty? (hash-map (frequency-hash x) 
                                                           (λ(k v) (if (> v 1) k '()))))])
-        (error (string-append (if (= (len duplicate-keys) 1) 
+        (error (string-append "members-unique? failed because " (if (= (len duplicate-keys) 1) 
                                   "item isn’t"
                                   "items aren’t") " unique:") duplicate-keys))
       result))
\ No newline at end of file
diff --git a/scribblings/list.scrbl b/scribblings/list.scrbl
new file mode 100644
index 0000000..d7517ef
--- /dev/null
+++ b/scribblings/list.scrbl
@@ -0,0 +1,76 @@
+#lang scribble/manual
+
+@(require scribble/eval (for-label racket sugar))
+
+@(define my-eval (make-base-eval))
+@(my-eval `(require sugar))
+
+@title{List}
+@defmodule[sugar/list]
+
+
+@defproc[
+(trimf
+[lst list?]
+[pred procedure?])
+list?]
+Drop elements from each end of @racket[_lst] that satisfy @racket[_pred]. Exactly equivalent to @racket[(dropf-right (dropf _lst _pred) _pred)].
+
+@examples[#:eval my-eval
+(trimf '(1 2 3 a b c 4 5 6) integer?)
+(trimf '(1 2 3 a b c) integer?)
+(trimf '(a b c) integer?)
+(trimf '(a b c 1 2 3 d e f) integer?)]
+
+
+@defproc[
+(filter-split
+[lst list?]
+[pred procedure?])
+(listof list?)]
+Like @racket[string-split], but for lists. Drop elements from anywhere in @racket[_lst] that satisfy @racket[_pred] — ends, middle, you name it — and return a list of the sublists that remain.
+
+@examples[#:eval my-eval
+(filter-split '(1 a b c 2 d e f 3) integer?)
+(filter-split '(1 a b c 2 d e f 3) (compose not integer?))
+(filter-split '(a b c 1 2 3 d e f) integer?)
+(filter-split '(a b c 1 2 3 d e f) (compose not integer?))]
+
+
+@defproc[
+(frequency-hash
+[lst list?])
+hash?]
+Count the frequency of each element in @racket[_lst], and return a hash whose keys are the unique elements of @racket[_lst], and each value is the frequency of that element within @racket[_lst].
+
+@examples[#:eval my-eval
+(frequency-hash '(a b b c c c))
+(frequency-hash '(c b c a b c))
+]
+
+
+
+@defproc[
+(members-unique?
+[container (or/c list? vector? string?)])
+boolean?]
+Return @racket[#t] if every element in @racket[_container] is unique, otherwise @racket[#f].
+
+@examples[#:eval my-eval
+(members-unique? '(a b c d e f))
+(members-unique? '(a b c d e f a))
+]
+
+@defproc[
+(members-unique?/error
+[container (or/c list? vector? string?)])
+boolean?]
+Same as @racket[members-unique?], but if the members are not unique, raises a descriptive error rather than returning @racket[#f].
+
+@examples[#:eval my-eval
+(members-unique?/error '(a b c d e f))
+(members-unique?/error '(a b c d e f a))
+(members-unique?/error '(a b c d e f a b))
+]
+
+
diff --git a/scribblings/sugar.scrbl b/scribblings/sugar.scrbl
index a5991b2..dcb252a 100644
--- a/scribblings/sugar.scrbl
+++ b/scribblings/sugar.scrbl
@@ -28,6 +28,8 @@ A collection of small functions to help make Racket code simpler & more readable
 
 @include-section["len.scrbl"]
 
+@include-section["list.scrbl"]
+
 @include-section["license.scrbl"]
 
 @index-section[]
diff --git a/tests.rkt b/tests.rkt
index 840cede..7134d94 100644
--- a/tests.rkt
+++ b/tests.rkt
@@ -93,9 +93,9 @@
 (check-false ("foobar" . ends-with? . "foo"))
 
 ;  (check-equal? (trim (list "\n" " " 1 2 3 "\n") whitespace?) '(1 2 3))
-(check-equal? (trim (list 1 3 2 4 5 6 8 9 13) odd?) '(2 4 5 6 8))
-;(check-equal? (splitf-at* '("foo" " " "bar" "\n" "\n" "ino") whitespace?) '(("foo")("bar")("ino")))
-(check-equal? (splitf-at* '(1 2 3 4 5 6) even?) '((1)(3)(5)))
+(check-equal? (trimf (list 1 3 2 4 5 6 8 9 13) odd?) '(2 4 5 6 8))
+;(check-equal? (filter-split '("foo" " " "bar" "\n" "\n" "ino") whitespace?) '(("foo")("bar")("ino")))
+(check-equal? (filter-split '(1 2 3 4 5 6) even?) '((1)(3)(5)))
 
 
 (check-equal? (filter-tree string? '(p)) null)