|
|
Scala example source code file (Course-2002-07.scala)
This example Scala source code file (Course-2002-07.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.
The Scala Course-2002-07.scala source code
//############################################################################
// Programmation IV - 2002 - Week 07
//############################################################################
object M0 {
trait Expr {
def isNumber: Boolean;
def isSum: Boolean;
def numValue: Int;
def leftOp: Expr;
def rightOp: Expr;
}
class Number(n: Int) extends Expr {
def isNumber: Boolean = true;
def isSum: Boolean = false;
def numValue: Int = n;
def leftOp: Expr = error("Number.leftOp");
def rightOp: Expr = error("Number.rightOp");
}
class Sum(e1: Expr, e2: Expr) extends Expr {
def isNumber: Boolean = false;
def isSum: Boolean = true;
def numValue: Int = error("Sum.numValue");
def leftOp: Expr = e1;
def rightOp: Expr = e2;
}
class Prod(e1: Expr, e2: Expr) extends Expr {
def isNumber: Boolean = false;
def isSum: Boolean = false;
def numValue: Int = error("Prod.numValue");
def leftOp: Expr = e1;
def rightOp: Expr = e2;
}
class Var(x: String) extends Expr {
def isNumber: Boolean = false;
def isSum: Boolean = false;
def numValue: Int = error("Var.numValue");
def leftOp: Expr = error("Var.leftOp");
def rightOp: Expr = error("Var.rightOp");
}
def eval(e: Expr): Int = {
if (e.isNumber) e.numValue
else if (e.isSum) eval(e.leftOp) + eval(e.rightOp)
else error("unknown expression")
}
def test = {
Console.println(" 0 = " + eval(new Number(0)));
Console.println(" 1 = " + eval(new Number(1)));
Console.println(" 0 + 1 = " +
eval(new Sum(new Number(0),new Number(1))));
Console.println(" 1 + 2 = " +
eval(new Sum(new Number(1),new Number(2))));
Console.println("2 + 3 + 4 = " +
eval(new Sum(new Sum(new Number(2),new Number(3)),new Number(4))));
Console.println;
}
}
//############################################################################
object M1 {
trait Expr {
def eval: Int;
}
class Number(n: Int) extends Expr {
def eval: Int = n;
}
class Sum(e1: Expr, e2: Expr) extends Expr {
def eval: Int = e1.eval + e2.eval;
}
def test = {
Console.println(" 0 = " + new Number(0).eval);
Console.println(" 1 = " + new Number(1).eval);
Console.println(" 0 + 1 = " +
new Sum(new Number(0),new Number(1)).eval);
Console.println(" 1 + 2 = " +
new Sum(new Number(1),new Number(2)).eval);
Console.println("2 + 3 + 4 = " +
new Sum(new Sum(new Number(2),new Number(3)),new Number(4)).eval);
Console.println;
}
}
//############################################################################
object M2 {
trait Expr;
case class Number(n: Int) extends Expr;
case class Sum(e1: Expr, e2: Expr) extends Expr;
def eval(e: Expr): Int = e match {
case Number(n) => n
case Sum(e1, e2) => eval(e1) + eval(e2)
}
def test = {
Console.println(" 0 = " + eval(Number(0)));
Console.println(" 1 = " + eval(Number(1)));
Console.println(" 0 + 1 = " + eval(Sum(Number(0),Number(1))));
Console.println(" 1 + 2 = " + eval(Sum(Number(1),Number(2))));
Console.println("2 + 3 + 4 = " + eval(Sum(Sum(Number(2),Number(3)),
Number(4))));
Console.println;
}
}
//############################################################################
object M3 {
trait Expr {
def eval: Int = this match {
case Number(n) => n
case Sum(e1, e2) => e1.eval + e2.eval
}
}
case class Number(n: Int) extends Expr;
case class Sum(e1: Expr, e2: Expr) extends Expr;
def test = {
Console.println(" 0 = " + Number(0).eval);
Console.println(" 1 = " + Number(1).eval);
Console.println(" 0 + 1 = " + Sum(Number(0),Number(1)).eval);
Console.println(" 1 + 2 = " + Sum(Number(1),Number(2)).eval);
Console.println("2 + 3 + 4 = " + Sum(Sum(Number(2),Number(3)),
Number(4)).eval);
Console.println;
}
}
//############################################################################
object M4 {
def concat[a](xss: List[List[a]]): List[a] = xss match {
case List() => List()
case xs :: xss1 => xs ::: concat(xss1)
}
def test_concat[a](xss: List[List[a]]) = {
Console.println(concat(xss).toString + " = concat(" + xss + ")"); // !!! .toString
}
def test = {
test_concat(List());
test_concat(List(List()));
test_concat(List(List(),List()));
test_concat(List(List(),List(),List()));
test_concat(List(List(1,2,3,4,5,6)));
test_concat(List(List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_concat(List(List(1,2,3),List(4,5,6)));
test_concat(List(List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_concat(List(List(1,2,3,4,5,6),List[Int](),List[Int]())); // !!! [int]
test_concat(List(List(1,2,3,4,5),List(6),List[Int]())); // !!! [int]
test_concat(List(List(1,2,3),List(4,5,6),List[Int]())); // !!! [int]
test_concat(List(List(1),List(2,3,4,5,6),List[Int]())); // !!! [int]
test_concat(List(List[Int](),List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_concat(List(List[Int](),List(1,2,3,4,5),List(6))); // !!! [int]
test_concat(List(List[Int](),List(1,2,3),List(4,5,6))); // !!! [int]
test_concat(List(List[Int](),List(1),List(2,3,4,5,6))); // !!! [int]
test_concat(List(List[Int](),List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_concat(List(List(1,2),List(3,4),List(5,6)));
Console.println;
}
}
//############################################################################
object M5 {
def zipFun[a,b](xs:List[a], ys:List[b]):List[Pair[a,b]] = Pair(xs,ys) match {
case Pair(List(), _) => List()
case Pair(_, List()) => List()
case Pair(x :: xs1, y :: ys1) => Pair(x, y) :: zipFun(xs1, ys1)
}
def test_zipFun[a,b](xs: List[a], ys: List[b]) = {
Console.println(zipFun(xs,ys).toString + " = zipFun(" + xs + "," + ys + ")"); // !!! .toString
}
def test = {
test_zipFun(List(),List());
test_zipFun(List(),List('a','b','c'));
test_zipFun(List(1,2,3),List());
test_zipFun(List(1),List('a'));
test_zipFun(List(1),List('a','b','c'));
test_zipFun(List(1,2,3),List('a'));
test_zipFun(List(1,2),List('a','b'));
test_zipFun(List(1,2),List('a','b','c'));
test_zipFun(List(1,2,3),List('a','b'));
test_zipFun(List(1,2,3),List('a','b','c'));
Console.println;
}
}
//############################################################################
object M6 {
def zipFun[a,b](xs:List[a], ys:List[b]):List[Pair[a,b]] = (Pair(xs,ys): @unchecked) match {
// !!! case Pair(List(), _), Pair(_, List()) => List()
case Pair(x :: xs1, y :: ys1) => Pair(x, y) :: zipFun(xs1, ys1)
}
def test_zipFun[a,b](xs: List[a], ys: List[b]) = {
Console.println(zipFun(xs,ys).toString + " = zipFun(" + xs + "," + ys + ")"); // !!! .toString
}
def test = {
test_zipFun(List(),List());
test_zipFun(List(),List('a','b','c'));
test_zipFun(List(1,2,3),List());
test_zipFun(List(1),List('a'));
test_zipFun(List(1),List('a','b','c'));
test_zipFun(List(1,2,3),List('a'));
test_zipFun(List(1,2),List('a','b'));
test_zipFun(List(1,2),List('a','b','c'));
test_zipFun(List(1,2,3),List('a','b'));
test_zipFun(List(1,2,3),List('a','b','c'));
Console.println;
}
}
//############################################################################
object M7 {
def heads[a](xss: List[List[a]]): List[a] = xss flatMap {
case x :: xs => List(x)
case List() => List()
}
def test_heads[a](xss: List[List[a]]) = {
Console.println(heads(xss).toString + " = heads(" + xss + ")"); // !!! .toString
}
def test = {
test_heads(List());
test_heads(List(List()));
test_heads(List(List(),List()));
test_heads(List(List(),List(),List()));
test_heads(List(List(1,2,3,4,5,6)));
test_heads(List(List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_heads(List(List(1,2,3,4,5,6),List[Int](),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_heads(List(List(1),List(2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1),List(2,3,4,5,6))); // !!! [int]
test_heads(List(List(1,2,3),List(4,5,6)));
test_heads(List(List(1,2,3),List(4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3),List(4,5,6))); // !!! [int]
test_heads(List(List(1,2,3,4,5),List(6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5),List(6))); // !!! [int]
test_heads(List(List(1,2),List(3,4),List(5,6)));
Console.println;
}
}
//############################################################################
object M8 {
def heads[a](xss: List[List[a]]): List[a] = xss.flatMap {
y => y match {
case x :: xs => List(x)
case List() => List()
}
}
def test_heads[a](xss: List[List[a]]) = {
Console.println(heads(xss).toString + " = heads(" + xss + ")"); // !!! .toString
}
def test = {
test_heads(List());
test_heads(List(List()));
test_heads(List(List(),List()));
test_heads(List(List(),List(),List()));
test_heads(List(List(1,2,3,4,5,6)));
test_heads(List(List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_heads(List(List(1,2,3,4,5,6),List[Int](),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List[Int](),List(1,2,3,4,5,6))); // !!! [int]
test_heads(List(List(1),List(2,3,4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1),List(2,3,4,5,6))); // !!! [int]
test_heads(List(List(1,2,3),List(4,5,6)));
test_heads(List(List(1,2,3),List(4,5,6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3),List(4,5,6))); // !!!
test_heads(List(List(1,2,3,4,5),List(6),List[Int]())); // !!! [int]
test_heads(List(List[Int](),List(1,2,3,4,5),List(6))); // !!! [int]
test_heads(List(List(1,2),List(3,4),List(5,6)));
Console.println;
}
}
//############################################################################
object M9 {
trait Expr {
def derive(v: Var): Expr = this match {
case Number(_) => Number(0)
case Var(name) => if (name == v.name) Number(1) else Number(0)
case Sum(e1, e2) => Sum(e1 derive v, e2 derive v)
case Prod(e1, e2) => Sum(Prod(e1, e2 derive v), Prod(e2, e1 derive v))
}
}
case class Number(x: Int) extends Expr {
override def toString = "Number(" + x + ")"; // !!! remove !
}
case class Var(name: String) extends Expr {
override def toString = "Var(" + name + ")"; // !!! remove !
}
case class Sum(e1: Expr, e2: Expr) extends Expr {
override def toString = "Sum(" + e1 + ", " + e2 + ")"; // !!! remove !
}
case class Prod(e1: Expr, e2: Expr) extends Expr {
override def toString = "Prod(" + e1 + ", " + e2 + ")"; // !!! remove !
}
def test = {
val x = Var("x");
val f0 = Prod(x, x);
val f1 = f0 derive x;
Console.println("f (x) = " + f0);
Console.println("f'(x) = " + f1);
Console.println;
}
}
//############################################################################
object MA {
def lookup[k,v](xs: List[Pair[k,v]], k: k): v = xs match {
case List() => error("no value for " + k)
case Pair(k1,v1) :: xs1 => if (k1 == k) v1 else lookup(xs1, k)
}
trait Expr {
def + (that: Expr) = Sum(this, that);
def * (that: Expr) = Prod(this, that);
def derive(v: Var): Expr = this match {
case Number(_) => Number(0)
case Var(name) => if (name == v.name) Number(1) else Number(0)
case Sum(e1, e2) => (e1 derive v) + (e2 derive v)
case Prod(e1, e2) => e1 * (e2 derive v) + e2 * (e1 derive v)
}
}
case class Number(x: Int) extends Expr {
override def toString = x.toString
}
case class Var(name: String) extends Expr {
override def toString = name;
}
case class Sum(e1: Expr, e2: Expr) extends Expr {
override def toString = e1.toString + " + " + e2.toString;
}
case class Prod(e1: Expr, e2: Expr) extends Expr {
override def toString = {
def factorToString(e: Expr) = e match {
case Sum(_, _) => "(" + e.toString + ")"
case _ => e.toString
}
factorToString(e1) + " * " + factorToString(e2);
}
}
def eval(e: Expr): Int = e match {
case Number(n) => n
case Var(_) => error("cannot evaluate variable")
case Sum(e1, e2) => eval(e1) + eval(e2)
case Prod(e1, e2) => eval(e1) * eval(e2)
}
def evalvars(xs: List[(String,Int)]): Expr => Int = {
def loop(e: Expr): Int = e match {
case Number(n) => n
case Var(name) => lookup(xs,name)
case Sum(e1, e2) => loop(e1) + loop(e2)
case Prod(e1, e2) => loop(e1) * loop(e2)
}
loop
}
def test = {
val x = Var("x");
val f0 = x * x;
val f1 = f0 derive x;
Console.println("f (x) = " + f0);
Console.println("f'(x) = " + f1);
val g0 = Number(2) * x * x + Number(3) * x;
val g1 = g0 derive x;
Console.println("g (x) = " + g0);
Console.println("g'(x) = " + g1);
Console.println("g (3) = " + evalvars(List(Pair("x",3)))(g0));
Console.println("g'(3) = " + evalvars(List(Pair("x",3)))(g1));
Console.println;
}
}
//############################################################################
object Utils {
private def power0(x: Int, y: Int): Int =
if (y == 1) x else if (y % 2 == 0) power0(x*x,y/2) else x*power0(x, y-1);
def power(x: Int, y: Int): Int = (x,y) match {
case Pair(0,0) => error("power(0,0)")
case Pair(0,_) => 0
case Pair(1,_) => 1
case Pair(_,0) => 1
case Pair(_,1) => x
case Pair(_,2) => x*x
case Pair(_,_) => if (y < 0) 1/power0(x,y) else power0(x,y)
}
def lookup(entries: List[(String,Int)], key: String): Int = entries match {
case List() => error("no value for " + key)
case Pair(k,v) :: _ if (k == key) => v
case _ :: rest => lookup(rest, key)
}
def compare(xs: List[String], ys: List[String]): Int = (xs, ys) match {
case Pair(List(), List()) => 0
case Pair(List(), _ ) => -1
case Pair(_ , List()) => +1
case Pair(x::xs , y::ys ) => {
val diff = x.compareTo(y);
if (diff != 0) diff else compare(xs,ys)
}
}
}
object MB {
import Utils._;
trait Expr {
private def count: Int = this match {
case Lit(n) => n
case Mul(Lit(n),_) => n
case _ => 1
}
private def term: Expr = this match {
case Lit(_) => Lit(1)
case Mul(Lit(_),r) => r
case _ => this
}
private def vars: List[String] = this match {
case Var(n) => List(n)
case Mul(l,r) => l.vars ::: r.vars
case Pow(l,n) => { val vs = l.vars; List.range(0,n).flatMap(i => vs) }
case _ => List()
}
private def +< (that: Expr): Boolean = (this +
Other Scala examples (source code examples)
Here is a short list of links related to this Scala Course-2002-07.scala source code file:
|
The search page
Other Scala source code examples at this package level
Click here to learn more about this project
