Typos in turtles (code and docs).

The name of the mathematician is Sierpinski.

* Serpinski => Sierpinski
* Rename serp => sierp.

collects/graphics/scribblings/traditional-turtles.scrbl

@@ -171,16 +171,16 @@ As the name says...}
   Draws a fractal that came up on an exam given at Rice in 1997 or so.
 }
 
-@defthing[serp-size real?]{
+@defthing[sierp-size real?]{
 
-A constant that is a good size for the @racket[serp] procedures.}
+A constant that is a good size for the @racket[sierp] procedures.}
 
 @deftogether[(
-@defproc[(serp [serp-size real?]) void?]
-@defproc[(serp-nosplit [serp-size real?]) void?]
+@defproc[(sierp [sierp-size real?]) void?]
+@defproc[(sierp-nosplit [sierp-size real?]) void?]
 )]{
 
-Draws the @as-index{Serpinski triangle} in two different ways, the
+Draws the @as-index{Sierpinski triangle} in two different ways, the
 first using @racket[split] heavily. After running the first one, try
 executing @racket[(draw 10)].}
 

collects/graphics/scribblings/value-turtles.scrbl

@@ -67,7 +67,7 @@ new turtles window.}
 @defproc[(merge [turtles1 turtles?] [turtles2 turtles?]) turtles?]{
 
 The @racket[split] and @racket[tprompt] forms provided by
-@racketmodname[graphics/turtles] isn't needed for
+@racketmodname[graphics/turtles] aren't needed for
 @racketmodname[graphics/value-turtles], since the turtles window is a
 value.
     

collects/graphics/turtle-examples.rkt

@@ -3,7 +3,7 @@
 (require graphics/turtles)
 
 (provide regular-poly regular-polys radial-turtles spaced-turtles
-         spokes spyro-gyra neato graphics-bexam serp-size serp serp-nosplit
+         spokes spyro-gyra neato graphics-bexam sierp-size sierp sierp-nosplit
          koch-size koch-split koch-draw lorenz lorenz1 peano-size
          peano-position-turtle peano fern-size fern1 fern2 gapped-lines)
 
@@ -91,9 +91,9 @@
          (turn/radians (/ pi 2)))
   (gb square-size))
 
-(define serp-size 120)
+(define sierp-size 120)
 
-(define (serp distance)
+(define (sierp distance)
   (define sqrt3 (sqrt 3))
   (define -2pi/3 (- 0 (/ (* 2 pi) 3)))
   (define pi/6 (/ pi 6))
@@ -128,7 +128,7 @@
   (turn/radians pi)
   (engine distance))
 
-(define (serp-nosplit distance)
+(define (sierp-nosplit distance)
   (define sqrt3 (sqrt 3))
   (define -2pi/3 (- 0 (/ (* 2 pi) 3)))
   (define pi/6 (/ pi 6))

collects/graphics/turtle-test.rkt

@@ -18,8 +18,8 @@
                            (move -150)
                            (turn/radians (- (/ pi 4)))
                            (graphics-bexam)))
-      ("Serpinski (split)" ,(lambda () (serp serp-size)))
-      ("Serpinski (no split)" ,(lambda () (serp-nosplit serp-size)))
+      ("Sierpinski (split)" ,(lambda () (sierp sierp-size)))
+      ("Sierpinski (no split)" ,(lambda () (sierp-nosplit sierp-size)))
       ("Koch (split)" ,(lambda () (koch-split koch-size)))
       ("Koch (no split)" ,(lambda () (koch-draw koch-size)))
       ("Lorenz Attractor" ,lorenz1)