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chapter14 tests
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‎src/chapter14/Currying.java

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package chapter14;
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import java.util.function.DoubleUnaryOperator;
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public class Currying {
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public static DoubleUnaryOperator curriedConverter(double f, double b) {
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return (double x) -> x * f + b;
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}
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}

‎src/chapter14/CurryingTest.java

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package chapter14;
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import static org.junit.Assert.*;
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import java.util.function.DoubleUnaryOperator;
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import org.junit.Test;
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public class CurryingTest {
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@Test
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public void test() {
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DoubleUnaryOperator fahrenheitConv = Currying.curriedConverter(9.0/5, 32);
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assertEquals(fahrenheitConv.applyAsDouble(25), (25* (9.0/5)+32), 1e-99);
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}
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}

‎src/chapter14/LinkedList.java

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package chapter14;
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import java.util.function.Predicate;
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import java.util.function.Supplier;
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interface MyList<T> {
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T head();
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MyList<T> tail();
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default boolean isEmpty() {
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return true;
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}
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default MyList<T> filter(Predicate<T> p) {
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return isEmpty() ?
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this :
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p.test(head()) ?
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new LazyList<T>(head(), () -> tail().filter(p)) :
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tail().filter(p);
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}
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}
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public class LinkedList<T> implements MyList<T> {
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private final T head;
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private final MyList<T> tail;
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public LinkedList(T head, MyList<T> tail) {
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this.head = head;
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this.tail = tail;
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}
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@Override
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public T head() {
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return head;
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}
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@Override
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public MyList<T> tail() {
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return tail;
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}
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public boolean isEmpty() {
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return false;
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}
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}
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class LazyList<T> implements MyList<T> {
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final T head;
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final Supplier<MyList<T>> tail;
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public LazyList(T head, Supplier<MyList<T>> tail) {
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this.head = head;
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this.tail = tail;
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}
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@Override
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public T head() {
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return head;
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}
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@Override
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public MyList<T> tail() {
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return tail.get();
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}
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public boolean isEmpty() {
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return false;
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}
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public static LazyList<Integer> from(int n) {
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return new LazyList(n, () -> from(n+1));
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}
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public static MyList<Integer> primes(MyList<Integer> numbers) {
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return new LazyList(numbers.head(), () -> primes(numbers.tail().filter(n -> n % numbers.head() != 0)));
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}
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}
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class Empty<T> implements MyList<T> {
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@Override
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public T head() {
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throw new UnsupportedOperationException();
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}
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@Override
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public MyList<T> tail() {
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throw new UnsupportedOperationException();
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}
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}

‎src/chapter14/LinkedListTest.java

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package chapter14;
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import static org.junit.Assert.*;
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import org.junit.Test;
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public class LinkedListTest {
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@Test
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public void test() {
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LinkedList<Integer> l = new LinkedList<>(5, new LinkedList<>(20, new Empty()));
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LazyList<Integer> lali = LazyList.from(2);
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int two = LazyList.primes(lali).head();
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int three = LazyList.primes(lali).tail().head();
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int five = LazyList.primes(lali).tail().tail().head();
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System.out.println(two + " " + three + " " + five);
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}
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}

‎src/chapter14/TrainJourney.java

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package chapter14;
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public class TrainJourney {
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public int price;
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public TrainJourney onward;
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public TrainJourney(int p, TrainJourney t) {
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price = p;
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onward = t;
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}
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static TrainJourney link(TrainJourney a, TrainJourney b) {
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/**
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* Destructive construction of linking
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*/
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if(a == null) {
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return b;
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}
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TrainJourney t = a;
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while(t.onward != null) {
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t = t.onward;
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}
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t.onward = b;
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return a;
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}
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static TrainJourney append(TrainJourney a, TrainJourney b) {
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/**
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* No mutation of data structures
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*/
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return a == null ? b : new TrainJourney(a.price, append(a.onward, b));
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}
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}

‎src/chapter14/Tree.java

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package chapter14;
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public class Tree {
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String key;
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int val;
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Tree left;
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Tree right;
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public Tree(String k, int v, Tree l, Tree r) {
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key = k; val = v; left = l; right = r;
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}
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}
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class TreeProcessor {
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public static int lookup(String k, int defaultval, Tree t) {
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if (t == null) return defaultval;
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if (k.equals(t.key)) return t.val;
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return lookup(k, defaultval, k.compareTo(t.key) < 0 ? t.left : t.right);
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}
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public static void update(String k, int v, Tree t) {
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if (t == null) {}
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else if (t.key == k) {t.val = v;}
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else {
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update(k, v, k.compareTo(t.key) < 0 ? t.left : t.right);
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}
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}
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public static Tree update1(String k, int v, Tree t) {
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if (t == null) {
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t = new Tree(k, v, null, null);
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}
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else if (t.key == k) {
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t.val = v;
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}
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else if (k.compareTo(t.key) < 0) {
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t.left = update1(k, v, t.left);
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}
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else {
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t.right = update1(k, v, t.right);
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}
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return t;
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}
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public static Tree fupdate(String k, int newval, Tree t) {
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return (t == null) ?
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new Tree(k, newval, null, null) :
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k.equals(t.key) ?
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new Tree(k, newval, t.left, t.right) :
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k.compareTo(t.key) < 0 ?
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new Tree(k, newval, fupdate(k, newval, t.left), t.right) :
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new Tree(k, newval, t.left, fupdate(k, newval, t.right));
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}
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}

‎src/chapter14/TreeTester.java

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package chapter14;
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import org.junit.Test;
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import java.lang.Math;
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public class TreeTester {
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@Test
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public void test() {
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Tree t = new Tree("abb", 12, null, null);
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String test = "a";
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for (int i = 0; i < 2000000; i++) {
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t = TreeProcessor.update1(String.valueOf(i), 2, t);
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}
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long start = System.currentTimeMillis();
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System.out.println("Searching for " + test);
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System.out.println(TreeProcessor.lookup(test, 0, t));
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long diff = System.currentTimeMillis() - start;
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System.out.println(diff + " milliseconds");
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}
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}

‎src/chapter14/visitor/BinOp.java

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package chapter14.visitor;
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public class BinOp extends Expr {
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Expr left;
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Expr right;
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public BinOp(String name, Expr left, Expr right) {
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this.name = name;
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this.left = left;
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this.right = right;
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}
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@Override
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public Expr accept(SimplifyExprVisitor v) {
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return v.visit(this);
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}
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public String toString() {
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return name + "(" + left.toString() + "," + right.toString() + ")";
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}
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}

‎src/chapter14/visitor/BinOpTest.java

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package chapter14.visitor;
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import static org.junit.Assert.*;
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import org.junit.Test;
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public class BinOpTest {
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@Test
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public void test() {
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Number ten = new Number("ten", 10);
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Number three = new Number("three", 3);
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Number zero = new Number("zero", 0);
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BinOp plus = new BinOp("+", ten, zero);
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BinOp plus2 = new BinOp("+", plus, three);
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BinOp plus3 = new BinOp("+", plus2, plus2);
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SimplifyExprVisitor v = new SimplifyExprVisitor();
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System.out.println(plus3);
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System.out.println(plus3.accept(v));
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}
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}

‎src/chapter14/visitor/Expr.java

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package chapter14.visitor;
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public abstract class Expr {
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protected String name;
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abstract public Expr accept(SimplifyExprVisitor v);
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public String getName() {
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return name;
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}
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}

‎src/chapter14/visitor/Number.java

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package chapter14.visitor;
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public class Number extends Expr {
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private int val;
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public int getVal() {
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return val;
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}
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public Number(String name, int val) {
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this.name = name;
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this.val = val;
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}
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@Override
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public Expr accept(SimplifyExprVisitor v) {
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// TODO Auto-generated method stub
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return null;
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}
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public String toString() {
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return String.valueOf(val);
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}
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}

‎src/chapter14/visitor/SimplifyExprVisitor.java

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package chapter14.visitor;
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public class SimplifyExprVisitor {
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public Expr visit(BinOp e) {
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if(e.getName().equals("+") && e.right instanceof Number) {
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if (((Number) e.right).getVal() == 0) {
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if (e.left instanceof BinOp) {
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return visit((BinOp) e.left);
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}
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else {
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return e.left;
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}
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}
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}
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if(e.getName().equals("+") && e.left instanceof Number) {
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if (((Number) e.left).getVal() == 0) {
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if (e.right instanceof BinOp) {
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return visit((BinOp) e.right);
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}
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else {
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return e.right;
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}
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}
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}
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if (e.left instanceof BinOp) {
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e.left = visit((BinOp) e.left);
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}
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if (e.right instanceof BinOp) {
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e.right = visit((BinOp) e.right);
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}
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return e;
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}
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}

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