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136 </table> |
136 </table> |
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138 <div class="overflow"> |
138 <div class="overflow"> |
139 <div class="sourcefirst"> line source</div> |
139 <div class="sourcefirst"> line source</div> |
140 |
140 <pre class="sourcelines"> |
141 <div class="parity0 source"><a href="#l1" id="l1"> 1</a> <span class="c">#!/usr/bin/env python</span></div> |
141 <span id="l1"><span class="c">#!/usr/bin/env python</span></span><a href="#l1"></a> |
142 <div class="parity1 source"><a href="#l2" id="l2"> 2</a> </div> |
142 <span id="l2"></span><a href="#l2"></a> |
143 <div class="parity0 source"><a href="#l3" id="l3"> 3</a> <span class="sd">"""Fun with generators. Corresponding Haskell implementation:</span></div> |
143 <span id="l3"><span class="sd">"""Fun with generators. Corresponding Haskell implementation:</span></span><a href="#l3"></a> |
144 <div class="parity1 source"><a href="#l4" id="l4"> 4</a> </div> |
144 <span id="l4"></span><a href="#l4"></a> |
145 <div class="parity0 source"><a href="#l5" id="l5"> 5</a> <span class="sd">primes = 2 : sieve [3, 5..]</span></div> |
145 <span id="l5"><span class="sd">primes = 2 : sieve [3, 5..]</span></span><a href="#l5"></a> |
146 <div class="parity1 source"><a href="#l6" id="l6"> 6</a> <span class="sd"> where sieve (p:ns) = p : sieve [n | n <- ns, mod n p /= 0]</span></div> |
146 <span id="l6"><span class="sd"> where sieve (p:ns) = p : sieve [n | n <- ns, mod n p /= 0]</span></span><a href="#l6"></a> |
147 <div class="parity0 source"><a href="#l7" id="l7"> 7</a> <span class="sd">"""</span></div> |
147 <span id="l7"><span class="sd">"""</span></span><a href="#l7"></a> |
148 <div class="parity1 source"><a href="#l8" id="l8"> 8</a> </div> |
148 <span id="l8"></span><a href="#l8"></a> |
149 <div class="parity0 source"><a href="#l9" id="l9"> 9</a> <span class="kn">from</span> <span class="nn">itertools</span> <span class="kn">import</span> <span class="n">dropwhile</span><span class="p">,</span> <span class="n">ifilter</span><span class="p">,</span> <span class="n">islice</span><span class="p">,</span> <span class="n">count</span><span class="p">,</span> <span class="n">chain</span></div> |
149 <span id="l9"><span class="kn">from</span> <span class="nn">itertools</span> <span class="kn">import</span> <span class="n">dropwhile</span><span class="p">,</span> <span class="n">ifilter</span><span class="p">,</span> <span class="n">islice</span><span class="p">,</span> <span class="n">count</span><span class="p">,</span> <span class="n">chain</span></span><a href="#l9"></a> |
150 <div class="parity1 source"><a href="#l10" id="l10"> 10</a> </div> |
150 <span id="l10"></span><a href="#l10"></a> |
151 <div class="parity0 source"><a href="#l11" id="l11"> 11</a> <span class="kn">def</span> <span class="nf">primes</span><span class="p">():</span></div> |
151 <span id="l11"><span class="kn">def</span> <span class="nf">primes</span><span class="p">():</span></span><a href="#l11"></a> |
152 <div class="parity1 source"><a href="#l12" id="l12"> 12</a> <span class="sd">"""Generate all primes."""</span></div> |
152 <span id="l12"> <span class="sd">"""Generate all primes."""</span></span><a href="#l12"></a> |
153 <div class="parity0 source"><a href="#l13" id="l13"> 13</a> <span class="kn">def</span> <span class="nf">sieve</span><span class="p">(</span><span class="n">ns</span><span class="p">):</span></div> |
153 <span id="l13"> <span class="kn">def</span> <span class="nf">sieve</span><span class="p">(</span><span class="n">ns</span><span class="p">):</span></span><a href="#l13"></a> |
154 <div class="parity1 source"><a href="#l14" id="l14"> 14</a> <span class="n">p</span> <span class="o">=</span> <span class="n">ns</span><span class="o">.</span><span class="n">next</span><span class="p">()</span></div> |
154 <span id="l14"> <span class="n">p</span> <span class="o">=</span> <span class="n">ns</span><span class="o">.</span><span class="n">next</span><span class="p">()</span></span><a href="#l14"></a> |
155 <div class="parity0 source"><a href="#l15" id="l15"> 15</a> <span class="c"># It is important to yield *here* in order to stop the</span></div> |
155 <span id="l15"> <span class="c"># It is important to yield *here* in order to stop the</span></span><a href="#l15"></a> |
156 <div class="parity1 source"><a href="#l16" id="l16"> 16</a> <span class="c"># infinite recursion.</span></div> |
156 <span id="l16"> <span class="c"># infinite recursion.</span></span><a href="#l16"></a> |
157 <div class="parity0 source"><a href="#l17" id="l17"> 17</a> <span class="kn">yield</span> <span class="n">p</span></div> |
157 <span id="l17"> <span class="kn">yield</span> <span class="n">p</span></span><a href="#l17"></a> |
158 <div class="parity1 source"><a href="#l18" id="l18"> 18</a> <span class="n">ns</span> <span class="o">=</span> <span class="n">ifilter</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">n</span><span class="p">:</span> <span class="n">n</span> <span class="o">%</span> <span class="n">p</span> <span class="o">!=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">ns</span><span class="p">)</span></div> |
158 <span id="l18"> <span class="n">ns</span> <span class="o">=</span> <span class="n">ifilter</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">n</span><span class="p">:</span> <span class="n">n</span> <span class="o">%</span> <span class="n">p</span> <span class="o">!=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">ns</span><span class="p">)</span></span><a href="#l18"></a> |
159 <div class="parity0 source"><a href="#l19" id="l19"> 19</a> <span class="kn">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="n">sieve</span><span class="p">(</span><span class="n">ns</span><span class="p">):</span></div> |
159 <span id="l19"> <span class="kn">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="n">sieve</span><span class="p">(</span><span class="n">ns</span><span class="p">):</span></span><a href="#l19"></a> |
160 <div class="parity1 source"><a href="#l20" id="l20"> 20</a> <span class="kn">yield</span> <span class="n">n</span></div> |
160 <span id="l20"> <span class="kn">yield</span> <span class="n">n</span></span><a href="#l20"></a> |
161 <div class="parity0 source"><a href="#l21" id="l21"> 21</a> </div> |
161 <span id="l21"></span><a href="#l21"></a> |
162 <div class="parity1 source"><a href="#l22" id="l22"> 22</a> <span class="n">odds</span> <span class="o">=</span> <span class="n">ifilter</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">i</span><span class="p">:</span> <span class="n">i</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span> <span class="n">count</span><span class="p">())</span></div> |
162 <span id="l22"> <span class="n">odds</span> <span class="o">=</span> <span class="n">ifilter</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">i</span><span class="p">:</span> <span class="n">i</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">1</span><span class="p">,</span> <span class="n">count</span><span class="p">())</span></span><a href="#l22"></a> |
163 <div class="parity0 source"><a href="#l23" id="l23"> 23</a> <span class="kn">return</span> <span class="n">chain</span><span class="p">([</span><span class="mi">2</span><span class="p">],</span> <span class="n">sieve</span><span class="p">(</span><span class="n">dropwhile</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">n</span><span class="p">:</span> <span class="n">n</span> <span class="o"><</span> <span class="mi">3</span><span class="p">,</span> <span class="n">odds</span><span class="p">)))</span></div> |
163 <span id="l23"> <span class="kn">return</span> <span class="n">chain</span><span class="p">([</span><span class="mi">2</span><span class="p">],</span> <span class="n">sieve</span><span class="p">(</span><span class="n">dropwhile</span><span class="p">(</span><span class="kn">lambda</span> <span class="n">n</span><span class="p">:</span> <span class="n">n</span> <span class="o"><</span> <span class="mi">3</span><span class="p">,</span> <span class="n">odds</span><span class="p">)))</span></span><a href="#l23"></a> |
164 <div class="parity1 source"><a href="#l24" id="l24"> 24</a> </div> |
164 <span id="l24"></span><a href="#l24"></a> |
165 <div class="parity0 source"><a href="#l25" id="l25"> 25</a> <span class="kn">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">"__main__"</span><span class="p">:</span></div> |
165 <span id="l25"><span class="kn">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">"__main__"</span><span class="p">:</span></span><a href="#l25"></a> |
166 <div class="parity1 source"><a href="#l26" id="l26"> 26</a> <span class="kn">import</span> <span class="nn">sys</span></div> |
166 <span id="l26"> <span class="kn">import</span> <span class="nn">sys</span></span><a href="#l26"></a> |
167 <div class="parity0 source"><a href="#l27" id="l27"> 27</a> <span class="kn">try</span><span class="p">:</span></div> |
167 <span id="l27"> <span class="kn">try</span><span class="p">:</span></span><a href="#l27"></a> |
168 <div class="parity1 source"><a href="#l28" id="l28"> 28</a> <span class="n">n</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span></div> |
168 <span id="l28"> <span class="n">n</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span></span><a href="#l28"></a> |
169 <div class="parity0 source"><a href="#l29" id="l29"> 29</a> <span class="kn">except</span> <span class="p">(</span><span class="ne">ValueError</span><span class="p">,</span> <span class="ne">IndexError</span><span class="p">):</span></div> |
169 <span id="l29"> <span class="kn">except</span> <span class="p">(</span><span class="ne">ValueError</span><span class="p">,</span> <span class="ne">IndexError</span><span class="p">):</span></span><a href="#l29"></a> |
170 <div class="parity1 source"><a href="#l30" id="l30"> 30</a> <span class="n">n</span> <span class="o">=</span> <span class="mi">10</span></div> |
170 <span id="l30"> <span class="n">n</span> <span class="o">=</span> <span class="mi">10</span></span><a href="#l30"></a> |
171 <div class="parity0 source"><a href="#l31" id="l31"> 31</a> <span class="n">p</span> <span class="o">=</span> <span class="n">primes</span><span class="p">()</span></div> |
171 <span id="l31"> <span class="n">p</span> <span class="o">=</span> <span class="n">primes</span><span class="p">()</span></span><a href="#l31"></a> |
172 <div class="parity1 source"><a href="#l32" id="l32"> 32</a> <span class="kn">print</span> <span class="s">"The first </span><span class="si">%d</span><span class="s"> primes: </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="nb">list</span><span class="p">(</span><span class="n">islice</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="n">n</span><span class="p">)))</span></div> |
172 <span id="l32"> <span class="kn">print</span> <span class="s">"The first </span><span class="si">%d</span><span class="s"> primes: </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="nb">list</span><span class="p">(</span><span class="n">islice</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="n">n</span><span class="p">)))</span></span><a href="#l32"></a></pre> |
173 <div class="sourcelast"></div> |
173 <div class="sourcelast"></div> |
174 </div> |
174 </div> |
175 </div> |
175 </div> |
176 </div> |
176 </div> |
177 |
177 |