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POUsing case class to display Expressions
 

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  1. POUsing case class to display Expressions
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    <p>I am trying to achieve the example shown in Martin Odersky's CourseRa Scala course to try and display expressions holding Sums/Prods using appropriate brackets. I came up with the below solution:</p> <pre><code>package expressions trait Expr { def eval : Int = { this match { case Number(n) =&gt; n case Sum(e1,e2) =&gt; e1.eval + e2.eval } } //def show( exp : Expr) : String } case class Number(n:Int) extends Expr case class Sum(e1: Expr, e2: Expr) extends Expr case class Prod(e1 : Expr, e2 : Expr) extends Expr case class Var(x:Char) extends Expr object testExpr { def show(exp : Expr) : String = { exp match { case Number(x) =&gt; x.toString() case Sum(e1, e2) =&gt; show(e1) + "+" + show(e2) case Prod(e1,e2) =&gt; val st1 = e1 match { case Sum(a,b) =&gt; "(" + show(Sum(a,b)) + ")" case _ =&gt; show(e1) } val st2 = e2 match { case Sum(a,b) =&gt; "(" + show(Sum(a,b)) + ")" case _ =&gt; show(e2) } st1 + "*" + st2 case Var(x) =&gt; x.toString } } } object test extends App{ println(testExpr.show(Sum(Number(1),Number(2)))) println(Sum(Number(1),Number(3)).eval) println(testExpr.show(Sum(Number(2),Prod(Number(10),Var('x'))))) println(testExpr.show(Sum(Prod(Number(2),Var('x')),Var('y')))) println(testExpr.show(Prod(Sum(Number(2),Var('x')),Var('y')))) println(testExpr.show(Prod(Sum(Number(2),Var('x')),Sum(Number(3),Var('y'))))) } </code></pre> <p>The way I am deciding on putting the brackets is definitely not the best solution. Can anyone suggest a better solution to achieve the same.</p> <p>Thanks and Regards, Paromita</p>
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    1. USParoTech
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    1. COAs per the Coursera Honor Code, you are not supposed to share solutions with other students. I suggest you delete this question.
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      1. USRobin Green
    2. COHi Robin, It is only a part of the practise exercises/examples used in the course. It is not part of any of the assignments in the course.
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