Scala example source code file (TestSyntax.scala)

This example Scala source code file (TestSyntax.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

app, bool, if, lit, lit, name, name, primdivide, primequals, primterm, primterm, string, term, term

The Scala TestSyntax.scala source code

package examples.parsing.lambda

/**
 * Parser for an untyped lambda calculus: abstract syntax tree
 *
 * @author Miles Sabin (adapted slightly by Adriaan Moors)
 */
trait TestSyntax 
{
  trait Term 
  
  case class Unit extends Term
  {
    override def toString = "unit"
  }
  
  case class Lit(n: int) extends Term
  {
    override def toString = n.toString
  }
  
  case class Bool(b: boolean) extends Term
  {
    override def toString = b.toString
  }
  
  case class Name(name: String) extends Term
  {
    override def toString = name
  }

  case class Ref(n: Name) extends Term
  {
    def value = n
  }
  
  case class Lam(n: Name, l: Term) extends Term
  {
    override def toString = "(\\ "+n+" -> "+l+")"
  } 
  
  case class App(t1: Term, t2: Term) extends Term
  {
    override def toString = "("+t1+" "+t2+")"
  } 
  
  case class Let(n: Name, t1: Term, t2: Term) extends Term
  {
    override def toString = "let "+n+" = "+t1+" in "+t2
  }
  
  case class If(c: Term, t1: Term, t2: Term) extends Term
  {
    override def toString = "if "+c+" then "+t1+" else "+t2
  }
  
  trait PrimTerm extends Term
  {
    def apply(n: Lit) : Term
  }

  case class PrimPlus extends PrimTerm
  {
    def apply(x: Lit) = new PrimTerm { def apply(y: Lit) = Lit(x.n+y.n) }
  }

  case class PrimMinus extends PrimTerm
  {
    def apply(x: Lit) = new PrimTerm { def apply(y: Lit) = Lit(x.n-y.n) }
  }
  
  case class PrimMultiply extends PrimTerm
  {
    def apply(x: Lit) = new PrimTerm { def apply(y: Lit) = Lit(x.n*y.n) }
  }

  case class PrimDivide extends PrimTerm
  {
    def apply(x: Lit) = new PrimTerm { def apply(y: Lit) = Lit(x.n/y.n) }
  }

  case class PrimEquals extends PrimTerm
  {
    def apply(x: Lit) = new PrimTerm { def apply(y: Lit) = Bool(x.n == y.n) }
  }
}