Lecture 15 and exercises

src/main/java/it/unimi/di/prog2/e15/IntRangeClient.java

@@ -0,0 +1,85 @@
+/*
+
+Copyright 2024 Massimo Santini
+
+This file is part of "Programmazione 2 @ UniMI" teaching material.
+
+This is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This material is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this file.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
+package it.unimi.di.prog2.e15;
+
+/** A class to test int ranges. */
+public class IntRangeClient {
+
+  /** . */
+  private IntRangeClient() {}
+
+  /**
+   * A method to test the {@link IntRange} class.
+   *
+   * <p>This methods reads the parameters of an {@link IntRange} from the lines in the standard
+   * input in the form {@code command value}, where the command is:
+   *
+   * <ul>
+   *   <li>{@code F} to set the from value of the range.
+   *   <li>{@code T} to set the to value of the range.
+   *   <li>{@code S} to set the step of the range.
+   * </ul>
+   *
+   * commands can be repeated, the last value is the one that is considered; the default values for
+   * from, to and step are respectively {@link Integer#MIN_VALUE}, {@link Integer#MAX_VALUE}, and 1.
+   * Once the input is exhausted, the method emits in a single line of the standard output:
+   *
+   * <ul>
+   *   <li>the number of integers in the range,
+   *   <li>the first integer in the range (if any),
+   *   <li>the last integer in the range (if different from the first).
+   * </ul>
+   *
+   * @param args not used.
+   */
+
+  /*- Uncomment and complete once you have implemented the range class
+
+    public static void main(String[] args) {
+      // declare the range...
+      try (Scanner sc = new Scanner(System.in)) {
+        while (sc.hasNext()) {
+          char command = sc.next().charAt(0);
+          int value = sc.nextInt();
+          switch (command) {
+            case 'F':
+              // set the from the range
+              break;
+            case 'T':
+              // set the to the range
+              break;
+            case 'S':
+              // set the step the range
+              break;
+            default:
+              throw new IllegalArgumentException("Unknown command: " + command);
+          }
+        }
+      }
+      int iterations = 0, first = 0, last = 0;
+      // complete...
+      System.out.println(
+          iterations + (iterations > 0 ? " " + first : "") + (iterations > 1 ? " " + last : ""));
+    }
+
+  */
+}

src/main/java/it/unimi/di/prog2/e15/StringIterators.java

@@ -0,0 +1,77 @@
+/*
+
+Copyright 2024 Massimo Santini
+
+This file is part of "Programmazione 2 @ UniMI" teaching material.
+
+This is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This material is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this file.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
+package it.unimi.di.prog2.e15;
+
+import java.util.Iterator;
+
+/** Utility class with some string iterators. */
+public class StringIterators {
+
+  /** . */
+  private StringIterators() {}
+
+  /**
+   * Filters even-positioned strings.
+   *
+   * @param it an iterator of strings.
+   * @return an iterator that returns the even-positioned strings of {@code it}.
+   */
+  public static Iterator<String> evenIterator(final Iterator<String> it) {
+    return new Iterator<>() {
+
+      // EXERCISE: complete the implementation
+
+      @Override
+      public boolean hasNext() {
+        throw new UnsupportedOperationException("Unimplemented method 'hasNext'");
+      }
+
+      @Override
+      public String next() {
+        throw new UnsupportedOperationException("Unimplemented method 'next'");
+      }
+    };
+  }
+
+  /**
+   * Converts strings to uppercase.
+   *
+   * @param it an iterator of strings.
+   * @return an iterator that returns the strings of {@code it} in uppercase.
+   */
+  public static Iterator<String> uppercase(final Iterator<String> it) {
+    return new Iterator<>() {
+
+      // EXERCISE: complete the implementation
+
+      @Override
+      public boolean hasNext() {
+        throw new UnsupportedOperationException("Unimplemented method 'hasNext'");
+      }
+
+      @Override
+      public String next() {
+        throw new UnsupportedOperationException("Unimplemented method 'next'");
+      }
+    };
+  }
+}

src/main/java/it/unimi/di/prog2/e15/StringIteratorsClient.java

@@ -0,0 +1,44 @@
+/*
+
+Copyright 2024 Massimo Santini
+
+This file is part of "Programmazione 2 @ UniMI" teaching material.
+
+This is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This material is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this file.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
+package it.unimi.di.prog2.e15;
+
+/** A class to test {@link StringIterators}. */
+public class StringIteratorsClient {
+
+  /** . */
+  private StringIteratorsClient() {}
+
+  /**
+   * Prints the uppercase version of the even lines of the standard input.
+   *
+   * @param args not used.
+   */
+  /*-  uncomment the following code once you have implemented the methods in StringIterators
+
+  public static void main(String[] args) {
+    try (Scanner s = new Scanner(System.in)) {
+      Iterator<String> it = StringIterators.uppercase(StringIterators.evenIterator(s));
+      while (it.hasNext()) System.out.println(it.next());
+    }
+  }
+  */
+}

src/main/java/it/unimi/di/prog2/e15/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * Esercizi relativi alla lezione 15, per maggiori dettagli si veda il <a
+ * href="https://prog2.di.unimi.it/diario">diario del corso</a>.
+ */
+package it.unimi.di.prog2.e15;

src/main/java/it/unimi/di/prog2/h14/IntSet.java

@@ -49,13 +49,6 @@ public class IntSet implements Iterable<Integer> {
    *
    */
 
-  private boolean repOk() {
-    for (int i = 0; i < els.size(); i++)
-      for (int j = 0; j < els.size(); j++)
-        if (i != j && els.get(i).equals(els.get(j))) return false;
-    return true;
-  }
-
   /**
    * Initializes this set to be empty.
    *
@@ -72,7 +65,7 @@ public IntSet() {
    * @param other the {@code IntSet} to copy from.
    */
   public IntSet(IntSet other) {
-    els = new ArrayList<Integer>(other.els);
+    els = new ArrayList<>(other.els);
     assert repOk();
   }
 
@@ -177,4 +170,16 @@ public String toString() {
   public Iterator<Integer> iterator() {
     return new IntGenerator(els);
   }
+
+  /**
+   * An implementation of the RI.
+   *
+   * @return whether the RI is satisfied.
+   */
+  private boolean repOk() {
+    for (int i = 0; i < els.size(); i++)
+      for (int j = 0; j < els.size(); j++)
+        if (i != j && els.get(i).equals(els.get(j))) return false;
+    return true;
+  }
 }

src/main/java/it/unimi/di/prog2/h14/IntSetsClient.java

@@ -25,6 +25,7 @@
 
 /** Classe per il test di {@link IntSet} {@link IntGenerator}. */
 public class IntSetsClient {
+  /** . */
   private IntSetsClient() {}
 
   /**

src/main/java/it/unimi/di/prog2/h14/Primes.java

@@ -28,6 +28,9 @@
 /** Iteratore che genera i numeri primi. */
 public class Primes implements Iterator<Integer> {
 
+  /** Crea un generatore di numeri primi. */
+  public Primes() {}
+
   /*-
    *  AF: il prossimo numero primo è il primo intero maggiore o uguale a
    *      candidate che non sia divisibile per uno dei primi già restituiti da next,

src/main/java/it/unimi/di/prog2/h15/DecimalDigits.java

@@ -0,0 +1,51 @@
+/*
+
+Copyright 2024 Massimo Santini
+
+This file is part of "Programmazione 2 @ UniMI" teaching material.
+
+This is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This material is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this file.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
+package it.unimi.di.prog2.h15;
+
+/** A class representing decimal digits of a long. */
+public class DecimalDigits {
+
+  /** The number whose digits are represented by this class. */
+  private final long number;
+
+  /**
+   * Creates a new instance representing the digits of the given number.
+   *
+   * @param number the number.
+   */
+  public DecimalDigits(final long number) {
+    this.number = number;
+  }
+
+  /**
+   * Returns the digit corresponding to the given power of 10.
+   *
+   * @param power the power.
+   * @return the corresponding digit.
+   */
+  public int digit(final int power) {
+    if (power < 0) throw new IllegalArgumentException("The power must be positive.");
+    long digit = number;
+    for (int i = 0; i < power; i++) digit /= 10;
+    return (int) (digit % 10);
+  }
+}

src/main/java/it/unimi/di/prog2/h15/DecimalDigitsAG.java

@@ -0,0 +1,73 @@
+/*
+
+Copyright 2024 Massimo Santini
+
+This file is part of "Programmazione 2 @ UniMI" teaching material.
+
+This is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This material is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this file.  If not, see <https://www.gnu.org/licenses/>.
+
+*/
+
+package it.unimi.di.prog2.h15;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * A class representing decimal digits of a long, endowed with a non zero digits iterator, based on
+ * an <strong>anonymous</strong> class.
+ */
+public class DecimalDigitsAG {
+
+  /** The number whose digits are represented by this class. */
+  private final long number;
+
+  /**
+   * Creates a new instance representing the digits of the given number.
+   *
+   * @param number the number.
+   */
+  public DecimalDigitsAG(final long number) {
+    this.number = number;
+  }
+
+  /**
+   * Returns a <em>generator</em> on from the least significant to the most significant non zero
+   * digits.
+   *
+   * @return the generator.
+   */
+  public Iterator<Integer> nonZeroDigits() {
+    // no need to pass any value, nor to define any named class
+    return new Iterator<Integer>() {
+
+      /** The remaining digits to return (except possibly for the trailing zeroes). */
+      private long remaining = number;
+
+      @Override
+      public boolean hasNext() {
+        while (remaining != 0 && remaining % 10 == 0) remaining /= 10;
+        return remaining != 0;
+      }
+
+      @Override
+      public Integer next() {
+        if (!hasNext()) throw new NoSuchElementException();
+        int digit = (int) (remaining % 10);
+        remaining /= 10;
+        return digit;
+      }
+    };
+  }
+}