diff --git a/cache.rkt b/cache.rkt
index d774a9c..23c3dd2 100644
--- a/cache.rkt
+++ b/cache.rkt
@@ -1,17 +1,24 @@
 #lang racket/base
 (require (for-syntax racket/base) "define.rkt")
 
+
 (define+provide+safe (make-caching-proc base-proc) 
   (procedure? . -> . procedure?)
   (let ([cache (make-hash)])
     (make-keyword-procedure
      (λ (kws kw-args . args)
-       (hash-ref! cache args (λ () (keyword-apply base-proc kws kw-args args)))))))
+       (hash-ref! cache (list* kws kw-args args) (λ () (keyword-apply base-proc kws kw-args args)))))))
+
+
+(define-for-syntax (lambdafy stx)
+  (syntax-case stx ()
+    [(_ (id arg ... . rest-arg) body ...)
+     #'(id (λ (arg ... . rest-arg) body ...))]
+    [(_ id body-exp)
+     #'(id body-exp)]))
+
 
 (provide+safe define/caching)
 (define-syntax (define/caching stx)
-  (syntax-case stx ()
-    [(_ (name arg ... . rest-arg) body ...)
-     #'(define/caching name (λ(arg ... . rest-arg) body ...))]
-    [(_ name body ...)
-     #'(define name (make-caching-proc body ...))]))
\ No newline at end of file
+  (with-syntax ([(id lambda-expr) (lambdafy stx)])
+    #'(define id (make-caching-proc lambda-expr))))
diff --git a/coerce.rkt b/coerce.rkt
index d18c92d..d402d32 100644
--- a/coerce.rkt
+++ b/coerce.rkt
@@ -1,165 +1,12 @@
 #lang racket/base
-(require (for-syntax racket/base racket/syntax))
-(require net/url racket/set racket/sequence "unstable/len.rkt" "define.rkt")
 
-(define-syntax-rule (make-coercion-error-handler target-format x)
-  (λ(e) (error (string->symbol (format "->~a" target-format)) (format "Can't convert ~s to ~a" x target-format))))
+(define-syntax-rule (r+p modname ...)
+  (begin
+    (begin
+      (require modname)
+      (provide (all-from-out modname))
+      (module+ safe
+        (require (submod modname safe))
+        (provide (all-from-out (submod modname safe))))) ...))
 
-
-(define+provide+safe (->int x)
-  (any/c . -> . integer?)
-  (with-handlers ([exn:fail? (make-coercion-error-handler 'int x)])
-    (cond
-      [(or (integer? x) (real? x)) (inexact->exact (floor x))]
-      [(complex? x) (->int (real-part x))]
-      [(string? x) (let ([strnum (string->number x)])
-                     (if (real? strnum) (->int strnum) (error 'ineligible-string)))]
-      [(or (symbol? x) (path? x) (bytes? x)) (->int (->string x))]
-      [(char? x) (char->integer x)]
-      [else (len x)]))) ; covers Lengthable types
-
-
-(define+provide+safe (->string x)
-  (any/c . -> . string?)
-  (if (string? x)
-      x ; fast exit for strings
-      (with-handlers ([exn:fail? (make-coercion-error-handler 'string x)])
-        (cond
-          [(or (equal? '() x) (void? x)) ""]
-          [(symbol? x) (symbol->string x)]
-          [(number? x) (number->string x)]
-          [(path? x) (path->string x)]
-          [(or (char? x) (bytes? x)) (format "~a" x)]
-          [(url? x) (url->string x)]
-          [else (error 'bad-type)]))))
-
-
-;; ->symbol, ->path, and ->url are just variants on ->string
-;; two advantages: return correct type, and more accurate error
-
-;; no need for "Symbolable" type - same as Stringable
-(define+provide+safe (->symbol x)
-  (any/c . -> . symbol?)
-  (if (symbol? x)
-      x
-      (with-handlers ([exn:fail? (make-coercion-error-handler 'symbol x)])
-        (string->symbol (->string x)))))
-
-
-(define+provide+safe (->path x)
-  (any/c . -> . path?)
-  (if (path? x)
-      x 
-      (with-handlers ([exn:fail? (make-coercion-error-handler 'path x)])
-        (cond 
-          [(url? x) (apply build-path (map path/param-path (url-path x)))]
-          [else (string->path (->string x))]))))
-
-
-(define+provide+safe (->url x)
-  (any/c . -> . url?) 
-  (with-handlers ([exn:fail? (make-coercion-error-handler 'url x)])
-    (string->url (->string x))))
-
-
-(define+provide+safe (->complete-path x)
-  (any/c . -> . complete-path?)
-  (with-handlers ([exn:fail? (make-coercion-error-handler 'complete-path x)])
-    (path->complete-path (->path x))))
-
-
-(define+provide+safe (->list x)
-  (any/c . -> . list?)
-  (if (list? x)
-      x
-      (with-handlers ([exn:fail? (make-coercion-error-handler 'list x)])
-        (cond 
-          [(string? x) (list x)]
-          [(vector? x) (for/list ([i (in-vector x)])
-                         i)]
-          [(set? x) (set->list x)]
-          ;; conditional sequencing relevant because hash also tests true for `sequence?`
-          [(hash? x) (hash->list x)]
-          [(integer? x) (list x)] ; because an integer tests #t for sequence?
-          [(sequence? x) (sequence->list x)]
-          ;[(stream? x) (stream->list x)] ;; no support for streams in TR
-          [else (list x)]))))
-
-
-(define+provide+safe (->vector x)
-  (any/c . -> . vector?)
-  (if (vector? x)
-      x
-      (with-handlers ([exn:fail? (make-coercion-error-handler 'vector x)])
-        (list->vector (->list x)))))
-
-
-(define+provide+safe (->boolean x)
-  (any/c . -> . boolean?)
-  (and x #t))
-
-
-;; coercion contracts & *ish predicates
-;; only make sense in untyped code
-;; thus they are here.
-(define-syntax-rule (make-blame-handler try-proc expected-sym)
-  (λ(b)
-    (λ(x)
-      (with-handlers ([exn:fail? (λ(e)
-                                   (raise-blame-error
-                                    b x
-                                    '(expected: "~a" given: "~e")
-                                    expected-sym x))])
-        (try-proc x)))))
-
-
-(provide+safe make-coercion-contract)
-(define-syntax (make-coercion-contract stx)
-  (syntax-case stx ()
-    [(_ stem coerce-proc)
-     (with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)]
-                   [can-be-stem? (format-id stx "can-be-~a?" #'stem)])
-       #'(make-contract
-          #:name 'coerce/stem?
-          #:projection (make-blame-handler coerce-proc 'can-be-stem?)))]
-    [(_ stem)
-     (with-syntax ([->stem (format-id stx "->~a" #'stem)])
-       #'(make-coercion-contract stem ->stem))]))
-
-
-(define-syntax (define+provide-coercion-contract stx)
-  (syntax-case stx ()
-    [(_ stem)
-     (with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)])
-       #'(begin
-           (provide+safe coerce/stem?)
-           (define coerce/stem? (make-coercion-contract stem))))]))
-
-
-(define+provide-coercion-contract int)
-(define+provide-coercion-contract string)
-(define+provide-coercion-contract symbol)
-(define+provide-coercion-contract path)
-(define+provide-coercion-contract boolean)
-(define+provide-coercion-contract list)
-
-
-(define-syntax (make-*ish-predicate stx)
-  (syntax-case stx ()
-    [(_ stem)
-     (with-syntax ([stemish? (format-id stx "~aish?" #'stem)]
-                   [->stem (format-id stx "->~a" #'stem)])
-       #`(begin
-           (provide+safe stemish?)
-           (define (stemish? x)
-             (with-handlers ([exn:fail? (λ(e) #f)]) (and (->stem x) #t)))))]))
-
-
-(make-*ish-predicate int)
-(make-*ish-predicate string)
-(make-*ish-predicate symbol)
-(make-*ish-predicate url)
-(make-*ish-predicate complete-path)
-(make-*ish-predicate path)
-(make-*ish-predicate list)
-(make-*ish-predicate vector)
\ No newline at end of file
+(r+p "coerce/base.rkt" "coerce/contract.rkt")
\ No newline at end of file
diff --git a/coerce/base.rkt b/coerce/base.rkt
new file mode 100644
index 0000000..4dccdb8
--- /dev/null
+++ b/coerce/base.rkt
@@ -0,0 +1,119 @@
+#lang racket/base
+(require (for-syntax racket/base racket/syntax))
+(require net/url racket/sequence "../unstable/len.rkt" "../define.rkt")
+
+(define-syntax-rule (make-coercion-error-handler target-format x)
+  (λ(e) (error (string->symbol (format "->~a" target-format)) (format "Can't convert ~s to ~a" x target-format))))
+
+
+(define+provide+safe (->int x)
+  (any/c . -> . integer?)
+  (with-handlers ([exn:fail? (make-coercion-error-handler 'int x)])
+    (cond
+      [(or (integer? x) (real? x)) (inexact->exact (floor x))]
+      [(complex? x) (->int (real-part x))]
+      [(string? x) (let ([strnum (string->number x)])
+                     (if (real? strnum) (->int strnum) (error 'ineligible-string)))]
+      [(or (symbol? x) (path? x) (bytes? x)) (->int (->string x))]
+      [(char? x) (char->integer x)]
+      [else (len x)]))) ; covers Lengthable types
+
+
+(define+provide+safe (->string x)
+  (any/c . -> . string?)
+  (if (string? x)
+      x ; fast exit for strings
+      (with-handlers ([exn:fail? (make-coercion-error-handler 'string x)])
+        (cond
+          [(or (null? x) (void? x)) ""]
+          [(symbol? x) (symbol->string x)]
+          [(number? x) (number->string x)]
+          [(path? x) (path->string x)]
+          [(or (char? x) (bytes? x)) (format "~a" x)]
+          [(url? x) (url->string x)]
+          [else (error 'bad-type)]))))
+
+
+;; ->symbol, ->path, and ->url are just variants on ->string
+;; two advantages: return correct type, and more accurate error
+
+;; no need for "Symbolable" type - same as Stringable
+(define+provide+safe (->symbol x)
+  (any/c . -> . symbol?)
+  (if (symbol? x)
+      x
+      (with-handlers ([exn:fail? (make-coercion-error-handler 'symbol x)])
+        (string->symbol (->string x)))))
+
+
+(define+provide+safe (->path x)
+  (any/c . -> . path?)
+  (if (path? x)
+      x 
+      (with-handlers ([exn:fail? (make-coercion-error-handler 'path x)])
+        (cond 
+          [(url? x) (apply build-path (map path/param-path (url-path x)))]
+          [else (string->path (->string x))]))))
+
+
+(define+provide+safe (->url x)
+  (any/c . -> . url?) 
+  (with-handlers ([exn:fail? (make-coercion-error-handler 'url x)])
+    (string->url (->string x))))
+
+
+(define+provide+safe (->complete-path x)
+  (any/c . -> . complete-path?)
+  (with-handlers ([exn:fail? (make-coercion-error-handler 'complete-path x)])
+    (path->complete-path (->path x))))
+
+
+(define+provide+safe (->list x)
+  (any/c . -> . list?)
+  (if (list? x)
+      x
+      (with-handlers ([exn:fail? (make-coercion-error-handler 'list x)])
+        (cond 
+          [(string? x) (list x)]
+          [(vector? x) (for/list ([i (in-vector x)])
+                         i)]
+          ;; conditional sequencing relevant because hash also tests true for `sequence?`
+          [(hash? x) (hash->list x)]
+          [(integer? x) (list x)] ; because an integer tests #t for sequence?
+          [(sequence? x) (sequence->list x)]
+          ;[(stream? x) (stream->list x)] ;; no support for streams in TR
+          [else (list x)]))))
+
+
+(define+provide+safe (->vector x)
+  (any/c . -> . vector?)
+  (if (vector? x)
+      x
+      (with-handlers ([exn:fail? (make-coercion-error-handler 'vector x)])
+        (list->vector (->list x)))))
+
+
+(define+provide+safe (->boolean x)
+  (any/c . -> . boolean?)
+  (and x #t))
+
+
+(define-syntax (make-*ish-predicate stx)
+  (syntax-case stx ()
+    [(_ stem)
+     (with-syntax ([stemish? (format-id stx "~aish?" #'stem)]
+                   [->stem (format-id stx "->~a" #'stem)])
+       #`(begin
+           (provide+safe stemish?)
+           (define (stemish? x)
+             (with-handlers ([exn:fail? (λ(e) #f)]) (and (->stem x) #t)))))]))
+
+
+(make-*ish-predicate int)
+(make-*ish-predicate string)
+(make-*ish-predicate symbol)
+(make-*ish-predicate url)
+(make-*ish-predicate complete-path)
+(make-*ish-predicate path)
+(make-*ish-predicate list)
+(make-*ish-predicate vector)
\ No newline at end of file
diff --git a/coerce/contract.rkt b/coerce/contract.rkt
new file mode 100644
index 0000000..d956491
--- /dev/null
+++ b/coerce/contract.rkt
@@ -0,0 +1,44 @@
+#lang racket/base
+(require (for-syntax racket/base racket/syntax) racket/contract "../define.rkt" "base.rkt")
+
+
+(define-syntax-rule (make-blame-handler try-proc expected-sym)
+  (λ(b)
+    (λ(x)
+      (with-handlers ([exn:fail? (λ(e)
+                                   (raise-blame-error
+                                    b x
+                                    '(expected: "~a" given: "~e")
+                                    expected-sym x))])
+        (try-proc x)))))
+
+
+(provide+safe make-coercion-contract)
+(define-syntax (make-coercion-contract stx)
+  (syntax-case stx ()
+    [(_ stem coerce-proc)
+     (with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)]
+                   [can-be-stem? (format-id stx "can-be-~a?" #'stem)])
+       #'(make-contract
+          #:name 'coerce/stem?
+          #:projection (make-blame-handler coerce-proc 'can-be-stem?)))]
+    [(_ stem)
+     (with-syntax ([->stem (format-id stx "->~a" #'stem)])
+       #'(make-coercion-contract stem ->stem))]))
+
+
+(define-syntax (define+provide-coercion-contract stx)
+  (syntax-case stx ()
+    [(_ stem)
+     (with-syntax ([coerce/stem? (format-id stx "coerce/~a?" #'stem)])
+       #'(begin
+           (provide+safe coerce/stem?)
+           (define coerce/stem? (make-coercion-contract stem))))]))
+
+
+(define+provide-coercion-contract int)
+(define+provide-coercion-contract string)
+(define+provide-coercion-contract symbol)
+(define+provide-coercion-contract path)
+(define+provide-coercion-contract boolean)
+(define+provide-coercion-contract list)
diff --git a/define.rkt b/define.rkt
index 3c15665..fa7036a 100644
--- a/define.rkt
+++ b/define.rkt
@@ -1,96 +1,92 @@
 #lang racket/base
-(require (for-syntax racket/base))
-(require racket/contract)
+(require (for-syntax racket/base racket/syntax syntax/strip-context) racket/contract)
 
-(provide (all-from-out racket/contract))
 
-;; get gets of typed source file, recompile it without typing in a submodule,
-;; then require those identifiers into the current level.
-(define-syntax (require-via-wormhole stx)
+(define-syntax (make-safe-module stx)
   (syntax-case stx ()
-    [(_ path-spec)
-     (let ([mod-name (gensym)])
-       ;; need to use stx as context to get correct require behavior
-       (datum->syntax stx `(begin
-                             (module mod-name typed/racket/base/no-check
-                               (require sugar/unstable/include)
-                               (include-without-lang-line ,(syntax->datum #'path-spec)))
-                             (require (quote mod-name)))))]))
-
-;; each define macro recursively converts any form of define
-;; into its lambda form (define name body ...) and then operates on that.
+    [(_ [id contract])
+     ;; need to put `racket/contract` inside calling location's context
+     (with-syntax ([require-racket-contract (datum->syntax #'id '(require racket/contract))])
+       #'(module+ safe 
+           require-racket-contract
+           (provide (contract-out [id contract]))))]
+    [(_ id)
+     #'(module+ safe
+         (provide id))]))
 
-(define-syntax (make-safe-module stx)
+
+;; convert calling pattern to form (id contract body-exp)
+(define-for-syntax (lambdafy-with-contract stx)
   (syntax-case stx ()
-    [(_ name contract)
-     #'(module+ safe 
-         (require racket/contract)
-         (provide (contract-out [name contract])))]
-    [(_ name)
-     #'(module+ safe 
-         (provide name))]))
+    [(_ (id arg ... . rest-arg) contract body ...)
+     (replace-context #'id  #'(id contract (λ (arg ... . rest-arg) body ...)))]
+    [(_ id contract lambda-exp)
+     (replace-context #'id #'(id contract lambda-exp))]))
 
-(define-syntax (define+provide+safe stx)
+
+;; convert calling pattern to form (id body-exp)
+(define-for-syntax (lambdafy stx)
   (syntax-case stx ()
-    [(_ (proc arg ... . rest-arg) contract body ...)
-     #'(define+provide+safe proc contract
-         (λ(arg ... . rest-arg) body ...))]
-    [(_ name contract body ...)
-     #'(begin
-         (define name body ...)
-         (provide name)
-         (make-safe-module name contract))]))
+    [(_ (id arg ... . rest-arg) body ...)
+     (replace-context #'id #'(id (λ (arg ... . rest-arg) body ...)))]
+    [(_ id lambda-exp)
+     (replace-context #'id #'(id lambda-exp))]))
+
+
+(define-syntax (define+provide+safe stx)
+  (with-syntax ([(id contract lambda-exp) (lambdafy-with-contract stx)])
+    #'(begin
+        (define id lambda-exp)
+        (provide id)
+        (make-safe-module [id contract]))))
+
 
 ;; for previously defined identifiers
-;; takes args like (provide+safe [ident contract]) or just (provide+safe ident)
+;; takes args like (provide+safe [id contract]) or just (provide+safe id)
 ;; any number of args.
-(define-syntax (provide+safe stx)
-  (syntax-case stx () 
-    [(_ items ...)
-     (datum->syntax stx
-                    `(begin
-                       ,@(for/list ([item (in-list (syntax->datum #'(items ...)))])
-                           (define-values (name contract) (if (pair? item)
-                                                              (values (car item) (cadr item))
-                                                              (values item #f)))
-                           `(begin
-                              (provide ,name)
-                              (make-safe-module ,name ,@(if contract (list contract) null))))))]))
+(define-syntax-rule (provide+safe thing ...)
+  (begin
+    (provide+safe/once thing) ...))
+
+
+;; `provide+safe` might have interleaved ids or [id contract] args so handle them individually.
+(define-syntax (provide+safe/once stx)
+  (with-syntax ([(id msm-arg) (syntax-case stx ()
+                                [(_ [id contract])
+                                 #'(id [id contract])]
+                                [(_ id)
+                                 #'(id id)])])
+    #'(begin
+        (provide id)
+        (make-safe-module msm-arg))))
+
 
 (define-syntax (define+provide/contract stx)
-  (syntax-case stx ()
-    [(_ (proc arg ... . rest-arg) contract body ...)
-     #'(define+provide/contract proc contract
-         (λ(arg ... . rest-arg) body ...))]
-    [(_ name contract body ...)
-     #'(begin
-         (provide (contract-out [name contract]))
-         (define name body ...))]))
+  (with-syntax* ([(id contract lambda-exp) (lambdafy-with-contract stx)]
+                 [require-racket-contract (datum->syntax #'id '(require racket/contract))])
+    #'(begin
+        require-racket-contract
+        (provide (contract-out [id contract]))
+        (define id lambda-exp))))
 
 
 (define-syntax (define/contract+provide stx)
-  (syntax-case stx ()
-    [(_ (proc arg ... . rest-arg) contract body ...)
-     #'(define/contract+provide proc contract
-         (λ(arg ... . rest-arg) body ...))]
-    [(_ name contract body ...)
-     #'(begin
-         (provide name)
-         (define/contract name contract body ...))]))
+  (with-syntax* ([(id contract lambda-exp) (lambdafy-with-contract stx)]
+                 [require-racket-contract (datum->syntax #'id '(require racket/contract))])
+    #'(begin
+        require-racket-contract
+        (provide id)
+        (define/contract id contract lambda-exp))))
 
 
 (define-syntax (define+provide stx)
-  (syntax-case stx ()
-    [(_ (proc arg ... . rest-arg) body ...)
-     #'(define+provide proc
-         (λ(arg ... . rest-arg) body ...))]
-    [(_ name body ...)
-     #'(begin
-         (provide name)
-         (define name body ...))]))
-
-(provide+safe require-via-wormhole
-              make-safe-module
+  (with-syntax ([(id lambda-exp) (lambdafy stx)])
+    #'(begin
+        (provide id)
+        (define id lambda-exp))))
+
+
+(provide+safe make-safe-module
               define+provide+safe
               provide+safe
               define+provide/contract
diff --git a/file.rkt b/file.rkt
index 5bfd899..9a37eae 100644
--- a/file.rkt
+++ b/file.rkt
@@ -1,10 +1,10 @@
 #lang racket/base
-(require "define.rkt" racket/set "coerce.rkt" racket/path "unstable/string.rkt")
+(require "define.rkt" "coerce/base.rkt" racket/path)
 
 
 ;; does path have a certain extension
 (define+provide+safe (has-ext? x ext)
-  (coerce/path? coerce/string? . -> . coerce/boolean?)
+  (pathish? stringish? . -> . boolean?)
   (define ext-of-path (filename-extension (->path x)))
   (->boolean (and ext-of-path (equal? (string-downcase (bytes->string/utf-8 ext-of-path)) (string-downcase (->string ext))))))
 
@@ -12,7 +12,7 @@
 ;; get file extension as a string, or return #f 
 ;; (consistent with filename-extension behavior)
 (define+provide+safe (get-ext x)
-  (coerce/path? . -> . (or/c #f string?))
+  (pathish? . -> . (or/c #f string?))
   (let ([fe-result (filename-extension (->path x))])
     (and fe-result (bytes->string/utf-8 fe-result))))
 
@@ -24,20 +24,26 @@
 
 
 (define+provide+safe (has-binary-ext? x)
-  (coerce/path? . -> . coerce/boolean?)
+  (pathish? . -> . boolean?)
   (let ([x (->path x)])
-    (ormap (λ(ext) (has-ext? x ext)) binary-extensions)))
+    (and (ormap (λ(ext) (has-ext? x ext)) binary-extensions) #t)))
 
 
 ;; put extension on path
 ;; use local contract here because this function is used within module
 (define+provide+safe (add-ext x ext)
-  (coerce/string? coerce/string? . -> . coerce/path?)
+  (stringish? stringish? . -> . pathish?)
   (->path (string-append (->string x) "." (->string ext))))
 
+
+(define (starts-with? str starter)
+  (define pat (regexp (format "^~a" (regexp-quote starter))))
+  (and (regexp-match pat str) #t))
+
+
 ;; take one extension off path
 (define+provide+safe (remove-ext x)
-  (coerce/path? . -> . path?)
+  (pathish? . -> . path?)
   ;; pass through hidden files (those starting with a dot)
   (let ([x (->path x)])
     (if ((->string x) . starts-with? . ".")
@@ -47,7 +53,7 @@
 
 ;; take all extensions off path
 (define+provide+safe (remove-ext* x)
-  (coerce/path? . -> . path?)
+  (pathish? . -> . path?)
   ;; pass through hidden files (those starting with a dot)
   (let ([x (->path x)])
     (if ((->string x) . starts-with? . ".")
diff --git a/info.rkt b/info.rkt
index 826d7b4..0b1dc1d 100644
--- a/info.rkt
+++ b/info.rkt
@@ -1,7 +1,7 @@
 #lang info
 (define collection "sugar")
-(define version "0.1")
-(define deps '("base" "rackunit-lib"))
+(define version "0.2")
+(define deps '("base"))
 (define build-deps '("scribble-lib" "racket-doc"))
 (define scribblings '(("scribblings/sugar.scrbl" ())))
 (define compile-omit-paths '("test"))
\ No newline at end of file
diff --git a/list.rkt b/list.rkt
index ed135a5..3e3456c 100644
--- a/list.rkt
+++ b/list.rkt
@@ -1,12 +1,11 @@
 #lang racket/base
-(require (for-syntax racket/base) racket/list racket/set racket/function)
-(require "unstable/len.rkt" "coerce.rkt" "define.rkt")
+(require (for-syntax racket/base) racket/list "define.rkt")
 
 (define (list-of-lists? xs) (and (list? xs) (andmap list? xs)))
 (define (index? x) (and (integer? x) (not (negative? x))))
 
-(define increasing-nonnegative? (λ(xs) (apply < -1 xs)))
-(define increasing-nonnegative-list? (and/c list? increasing-nonnegative?))
+(define increasing-nonnegative-list? (λ(x) (and (list? x) (or (empty? x)
+                                                              (apply < -1 x)))))
 
 (define (integers? x) (and (list? x) (andmap integer? x)))
 
@@ -65,7 +64,6 @@
 
 
 (define+provide+safe (slice-at xs len [force? #f])
-  ;; with polymorphic function, use cased typing to simulate optional position arguments 
   ((list? (and/c integer? positive?)) (boolean?) . ->* . list-of-lists?)
   (define-values (last-list list-of-lists)
     (for/fold ([current-list empty][list-of-lists empty])
@@ -100,14 +98,20 @@
        (hash-update! counter item (λ(v) (add1 v)) (λ _ 0)))
   counter)
 
+(define (->list x)
+  (cond
+    [(list? x) x]
+    [(vector? x) (vector->list x)]
+    [(string? x) (string->list x)]
+    [else (error '->list)]))
+
 
 (define+provide+safe (members-unique? x)
-  ((or/c list? vector? string?) . -> . boolean?)  
-  (cond 
-    [(list? x) (= (len (remove-duplicates x)) (len x))]
-    [(vector? x) (members-unique? (->list x))]
-    [(string? x) (members-unique? (string->list x))]
-    [else (error (format "members-unique? cannot be determined for ~a" x))]))
+  ((or/c list? vector? string?) . -> . boolean?)
+  (let ([x (->list x)])
+    (cond 
+      [(list? x) (= (length (remove-duplicates x)) (length x))]
+      [else (error (format "members-unique? cannot be determined for ~a" x))])))
 
 
 (define+provide+safe (members-unique?/error x)
@@ -116,7 +120,7 @@
   (if (not result)
       (let* ([duplicate-keys (filter-not empty? (hash-map (frequency-hash (->list x)) 
                                                           (λ(element freq) (if (> freq 1) element '()))))])
-        (error (string-append "members-unique? failed because " (if (= (len duplicate-keys) 1) 
+        (error (string-append "members-unique? failed because " (if (= (length duplicate-keys) 1) 
                                                                     "item isn't"
                                                                     "items aren't") " unique:") duplicate-keys))
       result))
@@ -137,10 +141,12 @@
 
 
 (define+provide+safe (break-at xs bps)
-  (list? (and/c coerce/list? (or/c empty? increasing-nonnegative-list?)) . -> . list-of-lists?)
+  (list? any/c . -> . list-of-lists?)
   (let ([bps (if (list? bps) bps (list bps))]) ; coerce bps to list
     (when (ormap (λ(bp) (>= bp (length xs))) bps)
       (error 'break-at (format "breakpoint in ~v is greater than or equal to input list length = ~a" bps (length xs))))
+    (when (not (increasing-nonnegative-list? bps))
+      (raise-argument-error 'break-at "increasing-nonnegative-list?" bps))
     ;; easier to do back to front, because then the list index for each item won't change during the recursion
     ;; cons a zero onto bps (which may already start with zero) and then use that as the terminating condition
     ;; because breaking at zero means we've reached the start of the list
diff --git a/main.rkt b/main.rkt
index 404fe9f..75a659d 100644
--- a/main.rkt
+++ b/main.rkt
@@ -1,18 +1,19 @@
 #lang racket/base
 
-(define-syntax-rule (r+p modname)
+(define-syntax-rule (r+p modname ...)
   (begin
-    (require modname)
-    (provide (all-from-out modname))
-    (module+ safe
-      (require (submod modname safe))
-      (provide (all-from-out (submod modname safe))))))
+    (begin
+      (require modname)
+      (provide (all-from-out modname))
+      (module+ safe
+        (require (submod modname safe))
+        (provide (all-from-out (submod modname safe))))) ...))
 
-(r+p "cache.rkt")
-(r+p "coerce.rkt")
-(r+p "debug.rkt")
-(r+p "define.rkt")
-(r+p "file.rkt")
-(r+p "list.rkt")
-(r+p "test.rkt")
-(r+p "xml.rkt")
\ No newline at end of file
+(r+p "cache.rkt"
+     "coerce.rkt"
+     "debug.rkt"
+     "define.rkt"
+     "file.rkt"
+     "list.rkt"
+     "test.rkt"
+     "xml.rkt")
\ No newline at end of file
diff --git a/unstable/len.rkt b/unstable/len.rkt
index 1d948c4..516e178 100644
--- a/unstable/len.rkt
+++ b/unstable/len.rkt
@@ -1,8 +1,8 @@
 #lang racket/base
-(require "../define.rkt" racket/set racket/sequence)
+(require "../define.rkt" racket/sequence)
 
 (define+provide+safe (len x)
-  ((or/c list? vector? set? sequence? string? symbol? path? hash?) . -> . integer?)
+  ((or/c list? vector? sequence? string? symbol? path? hash?) . -> . integer?)
   (cond
     [(list? x) (length x)]
     [(string? x) (string-length x)]
@@ -10,13 +10,12 @@
     [(path? x) (len (path->string x))]
     [(vector? x) (vector-length x)]
     [(hash? x) (len (hash-keys x))]
-    [(set? x) (len (set->list x))]
     [(and (sequence? x) (not (integer? x))) (len (sequence->list x))]
     [else (error "len: can't calculate length of" x)]))
 
 
 (module+ test
-  (require rackunit)
+  (require rackunit racket/set)
    (check-equal? (len '(1 2 3)) 3)
  (check-not-equal? (len '(1 2)) 3) ; len 2
  (check-equal? (len "foo") 3)
diff --git a/xml.rkt b/xml.rkt
index 4ed4a5f..22dfeef 100644
--- a/xml.rkt
+++ b/xml.rkt
@@ -4,12 +4,15 @@
 
 (define+provide+safe (xml-string->xexprs str)
   (string? . -> . (values xexpr? xexpr?))
-  (define xml-doc (with-input-from-string str (λ _ (permissive-xexprs #t) (read-xml))))
+  (define xml-doc (with-input-from-string str
+                                          (λ () (permissive-xexprs #t) (read-xml))))
   (values (xml->xexpr (document-prolog xml-doc)) (xml->xexpr (document-element xml-doc))))
 
+
 (define+provide+safe (xexprs->xml-string prolog-xexpr root-xexpr)
   (xexpr? xexpr? . -> . string?)
-  (with-output-to-string (λ _ (write-xml (document (xexpr->xml prolog-xexpr) (xexpr->xml root-xexpr) null)))))
+  (with-output-to-string (λ () (write-xml (document (xexpr->xml prolog-xexpr) (xexpr->xml root-xexpr) null)))))
+
 
 (module+ test
   (require rackunit)
@@ -18,4 +21,4 @@
   (define-values (str-prolog str-doc) (xml-string->xexprs str))
   (check-equal? str-prolog (prolog (list (p-i (location 1 0 1) (location 1 38 39) 'xml "version=\"1.0\" encoding=\"utf-8\"")) #f null))
   (check-equal? str-doc '(root () "hello world"))
-  (check-equal? (xexprs->xml-string str-prolog str-doc) str))
\ No newline at end of file
+  (check-equal? (xexprs->xml-string str-prolog str-doc) str))