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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) }
}
}
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