Lecture Notes for May 8
Roger Midmore

Final Exam 5/17 Wed. 12:25-2:25 Noland

Contributions of Pizza To Java's Design
---------------------------------------
1. Parametric Polymorphism
2. Bounded Polymorphism
3. First Class Functions
4. Algebraic Data Types

Polymorphism
------------
Pizza added Polymorphism to make it's code more reusable

Interface Comparable<T>{
  boolean equals(Object O);
  boolean less(Object O);
}

Class LinkedList<T> implements Comparable<T>{
 T value;
 LinkedList<T> next;
}

calling  the constructor will set both LinkedList<T>
and Comparable<T> to what ever dataType you want.

LinkedList<int> L1=new LinkedList(123);

First Class Functions
---------------------

Class Fct{
 static int f(int i){return 2+i;}
}

First Class Functions are called like in ML
Fun(T1,T2,T3)->T0

val static (int)->int g=f;
static int call((int)->int f, int i)
       return f(i);

They take the form of
(T1,a1,T2,a2,..)->T0
{ body }

delayed evaluation
static(int)->int Compose((int)->int f,(int)->int g){
  Fun(int i)->int{ return f(g(i));}

Algebraic Data Types
--------------------
in ML they take the form 
'a List=null|node of ('a*'a List)

in Pizza
Class List{
 case nil;
 case node(char head,List tail);
 int Length(){
     switch(this)
     case nil=return 0;
     case node(T,List<T> t)
	  return 1+t.length;
}

Enumeration
-----------
Class color{
  case red;
  case blue;
  case green;
  String toString(){
       switch(this)
       case=red return "red";
       case=blue return "blue";
       case=green return "green";
       }
}