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<link type="text/css" rel="stylesheet" href="http://pasterack.org/scribble.css"/><link type="text/css" rel="stylesheet" href="http://pasterack.org/racket.css"/><link type="text/css" rel="stylesheet" href="http://fonts.googleapis.com/css?family=Droid+Sans+Mono"/><div style="font-family:'Droid Sans Mono',monospace;background-color:transparent"><ol start="0" style="font-size:70%;color:#A0A0A0"><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><a class="RktModLink" data-pltdoc="x" href="http://docs.racket-lang.org/guide/Module_Syntax.html#%28part._hash-lang%29"><span class="RktMod">#lang</span></a><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><a class="RktModLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/index.html"><span class="RktSym">racket</span></a><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktCmt">;</span><span class="hspace"> </span><span class="RktCmt">A</span><span class="hspace"> </span><span class="RktCmt">picture</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29">require</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">2htdp/image</span><span class="RktPn">)</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29">define</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym">sierpinski</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">[</span><span class="RktSym">n</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktVal">8</span><span class="RktPn">]</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">[</span><span class="RktSym">t-size</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktVal">2</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29">cond</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/number-types.html#%28def._%28%28quote._~23~25kernel%29._zero~3f%29%29">zero?</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">n</span><span class="RktPn">)</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/teachpack/2htdpimage.html#%28def._%28%28lib._2htdp%2Fimage..rkt%29._triangle%29%29">triangle</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t-size</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/quote.html#%28form._%28%28quote._~23~25kernel%29._quote%29%29">'</a></span><span class="RktSym">solid</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/quote.html#%28form._%28%28quote._~23~25kernel%29._quote%29%29">'</a></span><span class="RktSym">darkgreen</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">[</span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._else%29%29">else</a></span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktStxLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29">define</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym">sierpinski</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/reference/generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._-%29%29"><span class="nobreak">-</span></a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">n</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t-size</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/teachpack/2htdpimage.html#%28def._%28%28lib._2htdp%2Fimage..rkt%29._freeze%29%29">freeze</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/teachpack/2htdpimage.html#%28def._%28%28lib._2htdp%2Fimage..rkt%29._above%29%29">above</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a class="RktValLink" data-pltdoc="x" href="http://docs.racket-lang.org/teachpack/2htdpimage.html#%28def._%28%28lib._2htdp%2Fimage..rkt%29._beside%29%29">beside</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">t</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktMeta"></span></span></li><li><span style="font-family:'Droid Sans Mono',monospace;font-size:125%"><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym">sierpinski</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktVal">8</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktMeta"></span></span></li></ol><p>=></p><blockquote><table style="font-size:90%;table-layout:fixed;width:100%;word-wrap:break-word"><tr><td><p><img alt="image" height="390" src="http://pasterack.org/14930.png" style="vertical-align: 0px; margin: -3px -3px -3px -3px;" width="518"/></p></td></tr></table></blockquote></div>
Sierpinski
#lang
racket
;
A
picture
(
require
2htdp/image
)
(
define
(
sierpinski
[
n
8
]
[
t-size
2
]
)
(
cond
[
(
zero?
n
)
(
triangle
t-size
'
solid
'
darkgreen
)
]
[
else
(
define
t
(
sierpinski
(
-
n
1
)
t-size
)
)
(
freeze
(
above
t
(
beside
t
t
)
)
)
]
)
)
(
sierpinski
8
2
)
=>
