code from 29.11 seminar

DigitalCathedral/Animal.cs

@@ -6,10 +6,16 @@ public class Animal : IEquatable<Animal>
     {
         private const double Epsilon = 1e-9;
 
-        private readonly int _value1;
+        private int _value1;
         private readonly double _value2;
         private readonly string _value3 = "My awesome string";
 
+        public void ChangeValue1()
+        {
+            var randomSource = new Random();
+            _value1 = randomSource.Next(-1000, 1001);
+        }
+
         public Animal(
             int value1,
             double value2,
@@ -47,7 +53,6 @@ public string GetValue3()
         public override int GetHashCode()
         {
             HashCode result = new HashCode();
-            result.Add(_value1);
             result.Add(_value2);
             result.Add(_value3);
             return result.ToHashCode();

DigitalCathedral/CombinatoricsExtensions.cs

@@ -0,0 +1,51 @@
+namespace DigitalCathedral;
+
+public static class CombinatoricsExtensions
+{
+
+    public static IEnumerable<IEnumerable<T>> GetCombinations<T>(
+        this IEnumerable<T> values,
+        int k,
+        IEqualityComparer<T> equalityComparer)
+    {
+        ThrowIfNotDistinctElements(values, equalityComparer);
+        throw new NotImplementedException();
+    }
+
+    public static IEnumerable<IEnumerable<T>> GetUniqueCombinations<T>(
+        this IEnumerable<T> values,
+        int k,
+        IEqualityComparer<T> equalityComparer)
+    {
+        ThrowIfNotDistinctElements(values, equalityComparer);
+        throw new NotImplementedException();
+    }
+
+    public static IEnumerable<IEnumerable<T>> GetSetOfAllSubsets<T>(
+        this IEnumerable<T> values,
+        IEqualityComparer<T> equalityComparer)
+    {
+        ThrowIfNotDistinctElements(values, equalityComparer);
+        throw new NotImplementedException();
+    }
+
+    public static IEnumerable<IEnumerable<T>> GetAllPermutations<T>(
+        this IEnumerable<T> values,
+        IEqualityComparer<T> equalityComparer)
+    {
+        ThrowIfNotDistinctElements(values, equalityComparer);
+        throw new NotImplementedException();
+    }
+
+    private static void ThrowIfNotDistinctElements<T>(
+        IEnumerable<T> values,
+        IEqualityComparer<T> equalityComparer)
+    {
+        var distinctValues = values.Distinct(equalityComparer).ToArray();
+        if (distinctValues.Length != values.Count())
+        {
+            throw new ArgumentException("Found equal elements in  collection.", nameof(values));
+        }
+    }
+
+}

DigitalCathedral/IntEqualityComparer.cs

@@ -0,0 +1,28 @@
+namespace DigitalCathedral;
+
+public sealed class IntEqualityComparer : IEqualityComparer<int>
+{
+    private const int EventIntHashCode = 0;
+
+    public bool Equals(
+        int x,
+        int y)
+    {
+        if (x % 2 == 0 && y % 2 == 0)
+        {
+            return true;
+        }
+
+        return x.Equals(y);
+    }
+
+    public int GetHashCode(
+        int obj)
+    {
+        if (obj % 2 == 0)
+        {
+            return EventIntHashCode;
+        }
+        return obj.GetHashCode();
+    }
+}

DigitalCathedral/Program.cs

@@ -243,28 +243,66 @@
 // Console.WriteLine(animal == animal2);
 // Console.WriteLine(animal.Equals(animal2));
 
+// var animal = new Animal(1, 1.1, "2.2");
+// Dictionary<Animal, string> collection = new Dictionary<Animal, string>();
+// collection.Add(animal, string.Empty);
+// var found = collection.TryGetValue(animal, out _);
+// animal.ChangeValue1();
+// found = collection.TryGetValue(animal, out _);
+// 
+// var collectionEnumerable = collection as IEnumerable<KeyValuePair<Animal, string>>;
+// var array = new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+// 
+// Console.WriteLine(Enumerable.Aggregate(Enumerable.Where(Enumerable.Select(array, x => x * 2), x => x % 3 == 0), 1, (accum, value) => accum * value));
+// 
+// Console.WriteLine(array.Select(x => x * 2)
+//     .Where(x => x % 3 == 0)
+//     .Aggregate(1, (accum, value) => accum * value));
+// 
+// 
+// 
+// foreach (var item in collection)
+// {
+//     // TODO: work with value
+// }
+// 
+// Student s1 = new Student("", "", "", "", "", 3);
+// Student s2 = new Student("", "", "", "", "", 3);
+// Console.WriteLine(s1.Equals(s2));
+// 
+// try
+// {
+//     Student st = new Student("Ivanov", "Ivan", "Ivanovich", "M1O-301B-21", "1234-123-12", 3);
+//     
+//     Console.WriteLine("No exceptions were thrown");
+// }
+// catch (ArgumentNullException ex)
+// {
+//     // 
+//     Console.WriteLine(ex.Message);
+// }
+// catch (ArgumentException ex)
+// {
+//     // 
+//     Console.WriteLine(ex.Message);
+// }
+// Console.WriteLine("after try/catch...");
+// 
+// var fraction = new Fraction(2, 5);
+// var fraction2 = new Fraction(1, 7);
+// Console.WriteLine(fraction.Equals(fraction2));
+// 
+// var multiplicationResult = Fraction.Multiplication(fraction, fraction2);
+// 
+// Console.WriteLine(fraction.CompareTo(fraction2));
+
 try
 {
-    Student st = new Student("Ivanov", "Ivan", "Ivanovich", "M1O-301B-21", "1234-123-12", 3);
-
-    Console.WriteLine("No exceptions were thrown");
-}
-catch (ArgumentNullException ex)
-{
-    // 
-    Console.WriteLine(ex.Message);
+    IEqualityComparer<int> equalityComparer = new IntEqualityComparer();
+    var values = Enumerable.Range(1, 10).ToArray();
+    values.GetCombinations(3, equalityComparer);
 }
 catch (ArgumentException ex)
 {
-    // 
     Console.WriteLine(ex.Message);
-}
-Console.WriteLine("after try/catch...");
-
-var fraction = new Fraction(2, 5);
-var fraction2 = new Fraction(1, 7);
-Console.WriteLine(fraction.Equals(fraction2));
-
-var multiplicationResult = Fraction.Multiplication(fraction, fraction2);
-
-Console.WriteLine(fraction.CompareTo(fraction2));
+}

DigitalCathedral/Student.cs

@@ -1,24 +1,25 @@
 namespace DigitalCathedral;
 
-public sealed class Student
+public sealed class Student:
+    IEquatable<Student>
 {
 
-    private string _surname;
-    private string _name;
-    private string _patronymic;
-    private string _group;
-    private string _zachetka;
-    private int _course;
+    private readonly string _surname;
+    private readonly string _name;
+    private readonly string _patronymic;
+    private readonly string _group;
+    private readonly string _zachetka;
+    private readonly int _course;
 
     public Student(
-        string surname,
-        string name,
-        string patronymic,
-        string group,
-        string zachetka,
+        string? surname,
+        string? name,
+        string? patronymic,
+        string? group,
+        string? zachetka,
         int course)
     {
-        if (surname == null)
+        if (surname is null)
         {
             throw new ArgumentNullException(nameof(surname));
         }
@@ -61,12 +62,46 @@ public override string ToString()
 
     public override int GetHashCode()
     {
-        return base.GetHashCode();
+        var result = new HashCode();
+        result.Add(_surname);
+        result.Add(_name);
+        result.Add(_patronymic);
+        result.Add(_group);
+        result.Add(_zachetka);
+        result.Add(_course);
+        return result.ToHashCode();
     }
 
-    public override bool Equals(object? obj)
+    public override bool Equals(
+        object? obj)
     {
-        return base.Equals(obj);
+        if (obj is null)
+        {
+            return false;
+        }
+
+        if (obj is Student student)
+        {
+            return Equals(student);
+        }
+
+        return false;
+    }
+
+    public bool Equals(
+        Student? student)
+    {
+        if (student is null)
+        {
+            return false;
+        }
+
+        return _surname.Equals(student._surname) &&
+               _name.Equals(student._name) &&
+               _patronymic.Equals(student._patronymic) &&
+               _group.Equals(student._group) &&
+               _zachetka.Equals(student._zachetka) &&
+               _course.Equals(student._course);
     }
 
 }