Add ease invert and reverse and fix cover

ease/main.scrbl

@@ -14,3 +14,4 @@ from one state into another gradually.
 source code: @url["https://github.com/jackfirth/racket-ease"]
 
 @scribble-include/no-subsection["private/base.scrbl"]
+@scribble-include/no-subsection["private/invert.scrbl"]

ease/private/base.rkt

@@ -25,7 +25,7 @@ module+ test
 
 (define (range-n start stop num-steps)
   (define step (/ (- stop start) num-steps))
-  (range start stop step))
+  (range start (+ stop step) step))
 
 
 (define (ease-real easing start stop num-steps)
@@ -41,4 +41,4 @@ module+ test
 
 module+ test
   (check-equal? (ease-real linear-ease 0 5 5)
-                '(0 1 2 3 4))
+                '(0 1 2 3 4 5))

ease/private/base.scrbl

@@ -9,8 +9,8 @@
                     [num-steps real?])
          (listof real?)]{
   Returns a list of intermediate values between @racket[start] and @racket[stop].
-  The number of values is equal to @racket[num-steps], and the a difference between
-  successive values is determined by @racket[easing].
+  The number of values is equal to @racket[num-steps] plus one, and the difference
+  between successive values is determined by @racket[easing].
   @ease-examples[
     (ease-real linear-ease 0 100 5)
 ]}

ease/private/invert.rkt

@@ -0,0 +1,36 @@
+#lang sweet-exp racket/base
+
+require racket/contract/base
+
+provide
+  contract-out
+    ease-invert (case-> (-> proper-ease/c proper-ease/c)
+                        (-> ease/c ease/c))
+    ease-reverse (case-> (-> proper-ease/c proper-ease/c)
+                         (-> ease/c ease/c))
+
+require "base.rkt"
+
+module+ test
+  require fancy-app
+          rackunit
+
+
+module+ test
+  (define (quadratic-ease-in x) (* x x))
+
+
+(define ((ease-invert easing) x)
+  (- 1 (easing (- 1 x))))
+
+module+ test
+  (check-equal? (ease-real (ease-invert quadratic-ease-in) 0 100 5)
+                (reverse (map (- 100 _) (ease-real quadratic-ease-in 0 100 5))))
+
+
+(define ((ease-reverse easing) x)
+  (easing (- 1 x)))
+
+module+ test
+  (check-equal? (ease-real (ease-reverse quadratic-ease-in) 0 100 5)
+                (reverse (ease-real quadratic-ease-in 0 100 5)))

ease/private/invert.scrbl

@@ -0,0 +1,21 @@
+#lang scribble/manual
+
+@(require "util/doc.rkt")
+
+
+@defproc[(ease-invert [easing ease/c]) ease/c]{
+  Returns an easing that is like @racket[easing], but
+  with proportional changes inverted from @racket[easing].
+  @ease-examples[
+    (define (quadratic-ease x) (* x x))
+    (ease-real quadratic-ease 0 100 5)
+    (ease-real (ease-invert quadratic-ease) 0 100 5)
+]}
+
+@defproc[(ease-reverse [easing ease/c]) ease/c]{
+  Returns an easing that is like @racket[easing], but
+  with it's steps reversed.
+  @ease-examples[
+    (ease-real linear-ease 0 100 5)
+    (ease-real (ease-reverse linear-ease) 0 100 5)
+]}

ease/private/main.rkt

@@ -3,8 +3,10 @@
 
 require
   "base.rkt"
+  "invert.rkt"
 
 
 provide
   all-from-out
     "base.rkt"
+    "invert.rkt"

info.rkt

@@ -18,3 +18,11 @@
     "racket-doc"
     "scribble-lib"
     "doc-coverage"))
+
+
+(define test-omit-paths
+  '("info.rkt"
+    "ease/info.rkt"
+    "ease/main.scrbl"
+    "private/base.scrbl"
+    "private/invert.scrbl"))