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    <p><strong>Removing and filtering List elements</strong></p> <p>In Scala you can filter the list to remove elements.</p> <pre><code>scala&gt; val courses = List("Artificial Intelligence", "Programming Languages", "Compilers", "Networks", "Databases") courses: List[java.lang.String] = List(Artificial Intelligence, Programming Languages, Compilers, Networks, Databases) </code></pre> <p>Let's remove a couple of classes:</p> <pre><code>courses.filterNot(p =&gt; p == "Compilers" || p == "Databases") </code></pre> <p>You can also use remove but it's deprecated in favor of filter or filterNot.</p> <p>If you want to remove by an index you can associate each element in the list with an ordered index using <code>zipWithIndex</code>. So, <code>courses.zipWithIndex</code> becomes:</p> <p><code>List[(java.lang.String, Int)] = List((Artificial Intelligence,0), (Programming Languages,1), (Compilers,2), (Networks,3), (Databases,4))</code></p> <p>To remove the second element from this you can refer to index in the Tuple with <code>courses.filterNot(_._2 == 1)</code> which gives the list:</p> <p><code>res8: List[(java.lang.String, Int)] = List((Artificial Intelligence,0), (Compilers,2), (Networks,3), (Databases,4))</code></p> <p>Lastly, another tool is to use <code>indexWhere</code> to find the index of an arbitrary element. </p> <p><code>courses.indexWhere(_ contains "Languages") res9: Int = 1</code></p> <p><strong>Re your update</strong></p> <blockquote> <p>I'm writing a function to remove the corresponding element from each lists, and all I know is that 1) the indices correspond and 2) the user inputs the course name. How can I remove the corresponding element from each list using filterNot?</p> </blockquote> <p>Similar to Nikita's update you have to "merge" the elements of each list. So courses, meridiems, days, and times need to be put into a Tuple or class to hold the related elements. Then you can filter on an element of the Tuple or a field of the class.</p> <p>Combining corresponding elements into a Tuple looks as follows with this sample data:</p> <pre><code>val courses = List(Artificial Intelligence, Programming Languages, Compilers, Networks, Databases) val meridiems = List(am, pm, am, pm, am) val times = List(100, 1200, 0100, 0900, 0800) val days = List(MWF, TTH, MW, MWF, MTWTHF) </code></pre> <p>Combine them with zip: </p> <p><code>courses zip days zip times zip meridiems</code></p> <p><code>val zipped = List[(((java.lang.String, java.lang.String), java.lang.String), java.lang.String)] = List((((Artificial Intelligence,MWF),100),am), (((Programming Languages,TTH),1200),pm), (((Compilers,MW),0100),am), (((Networks,MWF),0900),pm), (((Databases,MTWTHF),0800),am))</code></p> <p>This abomination flattens the nested Tuples to a Tuple. There are better ways.</p> <p><code>zipped.map(x =&gt; (x._1._1._1, x._1._1._2, x._1._2, x._2)).toList</code></p> <p>A nice list of tuples to work with.</p> <p><code>List[(java.lang.String, java.lang.String, java.lang.String, java.lang.String)] = List((Artificial Intelligence,MWF,100,am), (Programming Languages,TTH,1200,pm), (Compilers,MW,0100,am), (Networks,MWF,0900,pm), (Databases,MTWTHF,0800,am))</code></p> <p>Finally we can filter based on course name using <code>filterNot</code>. e.g. <code>filterNot(_._1 == "Networks")</code></p> <p><code>List[(java.lang.String, java.lang.String, java.lang.String, java.lang.String)] = List((Artificial Intelligence,MWF,100,am), (Programming Languages,TTH,1200,pm), (Compilers,MW,0100,am), (Databases,MTWTHF,0800,am))</code></p>
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    1. POHow can I idiomatically "remove" a single element from a list in Scala and close the gap?
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    1. COI added some details to the OP. I understand you're not my prof, but could you show me how to what I want to do?
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