Homework 5

1. Reimplement Homework 1 in Scala.
   • Expr becomes an abstract class with an undefined method def value: T
   • Use case classes for Const, Sum, Product
   • Rand and Read are objects
   • Use Seq[T] => T instead of the Function interface
   • Use varargs for the Sum, Product, and Op.
   • Put all your classes into an object hw5part1 in a file src/main/scala/hw5part1.scala.
   • Here is a test suite.
2. • Make an object hw5part2 and copy your definitions of Expr, Const, Op, Sum, Product. (We don't need Rand and Read.)
   • Add a case class Var, like Variable in the lab of lecture 8, but make it generic.
   • Rename the value method in Expr[T] to eval, with a parameter symbols: Map[String, T], like in the lab. If a variable doesn't exist in the symbol table, it's ok to throw an exception.
   • Define Def like Definition in the lab, but make it generic. Define eval[T](d: Def[T], symbols: Map[String, T])
   • Here is a test suite.
3. • Make a file hw5part3.scala. Include the SimpleLanguageParser and eval function from the Lecture 9 lab. In the grammar, allow variables (which you can parse with ident from JavaTokenParsers). Add a parameter symbols: Map[String, Int] to eval for evaluating such variables.
   • Here is a test suite.