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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The “L” must be a list of list. Like:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">1> L = [[1,2,3],[a,b,c]].<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[[1,2,3],[a,b,c]]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">2> [X || L1 <- L, X <- L1].<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">[1,2,3,a,b,c]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">3><o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> erlang-questions-bounces@erlang.org [mailto:erlang-questions-bounces@erlang.org]
<b>On Behalf Of </b>Carlos Suarez Fontalvo<br>
<b>Sent:</b> Wednesday, January 14, 2015 1:06 PM<br>
<b>To:</b> erlang-questions@erlang.org<br>
<b>Subject:</b> [erlang-questions] Lists Comprehension issue?<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Hi. I've reading this documentation:
<a href="http://www.erlang.org/doc/programming_examples/list_comprehensions.html">
http://www.erlang.org/doc/programming_examples/list_comprehensions.html</a><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">And it says that<o:p></o:p></p>
<h3><a name="id64520">3.5 Simplifications with List Comprehensions</a><o:p></o:p></h3>
<p>As an example, list comprehensions can be used to simplify some of the functions in lists.erl:<o:p></o:p></p>
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<pre>append(L) -> [X || L1 <- L, X <- L1].<o:p></o:p></pre>
<pre>map(Fun, L) -> [Fun(X) || X <- L].<o:p></o:p></pre>
<pre style="margin-bottom:12.0pt">filter(Pred, L) -> [X || X <- L, Pred(X)].<o:p></o:p></pre>
<pre style="margin-bottom:12.0pt"><span style="font-family:"Arial","sans-serif"">However when I tried to test this first example "append" doing something simple like this:<br><br>73> [X || L1 <- 20, X <- L1].<br>** exception error: bad generator 20</span><o:p></o:p></pre>
<pre style="margin-bottom:12.0pt"><span style="font-family:"Arial","sans-serif"">I got a "exception error" message. Any idea why?. Am I not considering something?</span><o:p></o:p></pre>
<pre><span style="font-family:"Arial","sans-serif"">Thanks in advance</span><o:p></o:p></pre>
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<p class="MsoNormal"><o:p> </o:p></p>
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