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    <p>An excellent explanation of the uses of the underscore is <em><a href="http://ananthakumaran.in/2010/03/29/scala-underscore-magic.html" rel="noreferrer">Scala _ [underscore] magic</a></em>.</p> <p>Examples:</p> <pre><code> def matchTest(x: Int): String = x match { case 1 =&gt; "one" case 2 =&gt; "two" case _ =&gt; "anything other than one and two" } expr match { case List(1,_,_) =&gt; " a list with three element and the first element is 1" case List(_*) =&gt; " a list with zero or more elements " case Map[_,_] =&gt; " matches a map with any key type and any value type " case _ =&gt; } List(1,2,3,4,5).foreach(print(_)) // Doing the same without underscore: List(1,2,3,4,5).foreach( a =&gt; print(a)) </code></pre> <p>In Scala, <code>_</code> acts similar to <code>*</code> in Java while importing packages.</p> <pre><code>// Imports all the classes in the package matching import scala.util.matching._ // Imports all the members of the object Fun (static import in Java). import com.test.Fun._ // Imports all the members of the object Fun but renames Foo to Bar import com.test.Fun.{ Foo =&gt; Bar , _ } // Imports all the members except Foo. To exclude a member rename it to _ import com.test.Fun.{ Foo =&gt; _ , _ } </code></pre> <p>In Scala, a getter and setter will be implicitly defined for all non-private vars in a object. The getter name is same as the variable name and <code>_=</code> is added for the setter name.</p> <pre><code>class Test { private var a = 0 def age = a def age_=(n:Int) = { require(n&gt;0) a = n } } </code></pre> <p>Usage:</p> <pre><code>val t = new Test t.age = 5 println(t.age) </code></pre> <p>If you try to assign a function to a new variable, the function will be invoked and the result will be assigned to the variable. This confusion occurs due to the optional braces for method invocation. We should use _ after the function name to assign it to another variable.</p> <pre><code>class Test { def fun = { // Some code } val funLike = fun _ } </code></pre>
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    1. POWhat are all the uses of an underscore in Scala?
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    1. COThat is a good explanation, but it doesn't even have all of them. It's missing ignored parameters/variables, joining letters and punctuation, existential types, higher kinded types
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