C# Language Object-oriented Programming Basics

Transcription

1 C# Language Object-oriented Programming Basics O 2 DES.NET Object-oriented Simulation and Optimization Algorithm (1) 2017 Li Haobin, ISEM Department,NUS 1

2 Syllabus 1. C# Language Object-oriented Programming Basics 2. O 2 DES.NET Discrete Event Simulation Modelling 3. System Decomposition and Modular Modelling 4. Mathematical Programming and Embedded Optimization Simulation 5. Simulation-based Search Optimization 6. Optimal Hash-rate Allocation and Parallel Computing 7. XML Data Storage and Graphical Presentation 2017 Li Haobin, ISEM Department,NUS 2

3 Why Programming? Experiment Tool Theoretical Science axiom assumption - > lemma - > theorem - > corollary Experimental Science Experimental science is science based on experimental research that plays the role of testing hypothesis, typically in controlled laboratory settings Li Haobin, ISEM Department,NUS 3

4 Why Programming? Knowledge Accumulation Thesis Source Code Research motivation Literature review Method discussion Introduction of achievements Study result deliverable Can be duplicated Can be applied Can be accumulated 2017 Li Haobin, ISEM Department,NUS 4

5 Why Programming? Technology Transformation Research Results Commercial Products Method Algorithm Framework Procedure Software System 2017 Li Haobin, ISEM Department,NUS 5

6 Why Object-oriented? Object-oriented Task model What to do? Linear thinking Input-> Output Object-oriented System Model What is it? Reticular thinking Entity Relationship Object-oriented Discrete event Model O 2 DES.NET 2017 Li Haobin, ISEM Department,NUS 6

7 Why using C#? Strongly-typed language, neat grammar and clear structure Inherit and develop advanced languages such as C++, JAVA, Pascal Compatible with collaborative development of complex system and avoid program error Strong reliability Abundant resources in standard library Maintenance and guarantee from commercial company Strong extensibility Derived from windows system, various application scenarios and peripheral devices, leading to wide applicability.net Core can be used for cross-platform development Development environment is powerful yet easy to use IntelliSense, auto code completion, indent function to help the development process 2017 Li Haobin, ISEM Department,NUS 7

8 C# Language Object-oriented Programming Basics 1. Main Data Types 2. Standard Data Structure 3. Input and Output Methods 4. Loop Structure 5. Conditional Structure 6. Function Method 7. Lambda Expression 8. LINQ Search C# only Basic Grammar 2017 Li Haobin, ISEM Department,NUS 8

9 C# Language Object-oriented Programming Basics 9. Encapsulation 10. Inheritance 11. Polymorphism 12. Interface OOP Basic Concept 1.13 Example: 24 Point Intellectual Program 2017 Li Haobin, ISEM Department,NUS 9

10 Basic Grammar 2017 Li Haobin, ISEM Department,NUS 10

11 1.1 Basic Data Type C# Key Words System Type Numerical Range Description Default Value bool System.Boolean true or f a lse Represents truth or falsity f a l se sbyte System.SByte -128 to 127 Signed 8-bit number 0 byte System.Byte 0 to 255 Unsigned 8-bit number 0 sh o rt System.Int16-32,768 to 32,767 Signed 16-bit number 0 ushort System.UInt16 0 to 65,535 Unsigned 16-bit number 0 i n t System.Int32-2,147,483,648 t o 2,147,483,647 Signed 32-bit number 0 u i n t System.UInt32 0 to 4,294,967,295 Unsigned 32-bit number 0 long System.Int64-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 Signed 64-bit number 0 ulong System.UInt64 0 to 18,446,744,073,709,551,615 Unsigned 64-bit number 0 char System.Char U+0000 to U + f f f f Single 16-bit Unicode character \0 f l o a t System.Single t o bit floating-pointnumber 0.0 double System.Double ± t o ± bit floating-pointnumber 0.0 decimal System.Decimal ( x t o 7.9 x )/(10 0 to 28 ) 128-bit signednumber 0 s t r i n g System.String Limited by system memory Represents a set of Unicode characters "" object System.Object Can store any data type i n an object variable The base class of all types in the.net universe n u l l 2017 Li Haobin, ISEM Department,NUS 11

12 1.1 Basic Data Type Enumeration Type: a data type consisting of a set of named values called elements, members, enumerals, or enumerators of the type. p u b l i c class EnumTest enum Days Sun, Mon, Tue, Wed, Thu, F r i, Sat ; static void Main() i n t x = (int)days.sun; i nt y=( int)days.fri; Console.WriteLine("Sun = 0", x ) ; Console.WriteLine("Fri =0", y ) ; /* Output: Sun = 0 Fri = 5 */ 2017 Li Haobin, ISEM Department,NUS 12

13 1.1 Basic Data Type n u l l Type: represents that no value is assigned static void M a in(string[] args) // Compiler e r r o r s! // Value types cannot be set t o n u l l! bool mybool = n u l l ; int myint = n u l l ; // Define some local nullable variables. int? n u l l a b l e I n t = 10; double? nullabledouble = 3.14; bool? nullablebool = n u l l ; char? nullablechar = 'a'; int?[] arrayofnullableints = new i n t? [ 1 0 ] ; // E r r o r! Strings are reference types! string? s = "oops"; Equivalent to // OK! Strings are reference types. s t r i n g mystring = n u l l ; // Define some local nullable types using Nullable<T>. Nullable<int> n u l l a b l e I n t = 10; Nullable<double> nullabledouble = 3.14; Nullable<bool> nullablebool = n u l l ; Nullable<char> nullablechar = ' a ' ; Nullable<int>[] arrayofnullableints = New Nullable<int>[10]; 2017 Li Haobin, ISEM Department,NUS 13

14 1.1 Basic Data Type System Type System.DateTime System.TimeSpan Description Represents a point of time, usually represents as date and time of day Represents a time interval Instantiation: Time Computation : DateTime date1 = new DateTime(2008, 3, 1, 7, 0, 0 ) ; Console.Writ eli ne(date 1.ToS tri ng()); // For en-us culture, displays 3/1/2008 7:00:00 AM DateTime departure = new DateTime(2010, 6, 12, 18, 32, 0); DateTime a r r i v a l = new DateTime(2010, 6, 13, 22, 47, 0 ) ; TimeSpan traveltime = a r r i v a l - departure; Console.WriteLine("0 - traveltime); 1 = 2", a r r i v a l, departure, // The example displays the f ollowing output: // 6/13/ :47:00 PM - 6/12/2010 6:32:00 PM = 1.04:15: Li Haobin, ISEM Department,NUS 14

15 1.2 Standard Data Structure: Array System Type System.Array Description Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime. Create and use an array: // Create and f i l l an array of 4 Integers int[] myints = new int[4]; myints[0] = 100; myints[1] = 200; myints[2] = 300; myints[3] = 400; // Now print each value. foreach ( int i in myints) Console.WriteLine(i); Console.WriteLine(); myints Initialization grammar: // Array initialization syntax using the new keyword. s t r i n g [] stringarray = new s t r i n g [ ] "one", "two", "three" ; Console.WriteLine("stringArray has 0 elements", stringarray.length); // Array initialization syntax without using the new keyword. bool[] boolarray = f a l s e, f a l s e, true ; Console.WriteLine("boolArray has 0 elements", boolarray.length); // Array initialization with new keyword and s ize. int[] intarray = new int[4] 20, 22, 23, 0 ; Console.WriteLine("intArray has 0 elements", intarray.length); Console.WriteLine(); Fixed size, fast and direct access based on index 2017 Li Haobin, ISEM Department,NUS 15

16 1.2 Standard Data Structure: List System Type System.Collections. Generic.List<T> Description Represents a strongly-typed list of an object that can be accessed by index. Provide methods for searching, sorting and manipulating lists. Create and use a list: Other common operations: // Create and f i l l a list of 4 Integers List<int> myints = new L i s t < i n t > ( ) ; myints.add(100); myints.add(200); myints.add(300); myints.add(400); // Now print each value. foreach ( int i in myints) Console.WriteLine(i); Console.WriteLine(); myints 0 // Add element to the end of the list myints.addrange(new List<int> 500, 600, 700 ); // Insert element into the specific index of List<T> myints.insert(2, 800); // Remove element from the specific index of List<T> myints.removeat(3); Unfixed size, flexible to add or remove elements 2017 Li Haobin, ISEM Department,NUS 16

17 1.2 Standard Data Structure:Queue and Stack System Type System.Collections.Queue<T> System.Collections.Generic.Stack<T> Queue Example: Description Represents a collection of first-in-first-out (FIFO) objects. Represents a collection of last-in-first-out (LIFO) objects that have variable size (Instantiation for the same specified type). Stack Example: // Creates and initializes a new Queue. Queue<int> myq = new Queue<int>(); myq.enqueue(100); myq.enqueue(200); myq.enqueue(300); // Displays the properties and values of the Queue. Console.WriteLine(myQ.Count); Console.WriteLine(myQ.Dequeue()); Console.WriteLine(myQ.Dequeue()); Console.WriteLine(myQ.Dequeue()); myq // Creates and initializes a new Stack. Stack<int> mystack = new Stack<int>(); mystack.push(100); mystack.push(200); mystack.push(300); // Displays the properties and values of the Stack. Console.WriteLine(myStack.Count); Console.WriteLine(myStack.Pop()); Console.WriteLine(myStack.Pop()); Console.WriteLine(myStack.Pop()); mystack Li Haobin, ISEM Department,NUS Unfixed size, fixed access mode 17

18 1.2 Standard Data Structure: Hash Set System Type System.Collections.Generic.HashSet<T> Description Represents a collection of values. Hash Set Example: // Creates and initializes a new hash set. HashSet<int> myset = new HashSet<int>(); myset.add(1); myset.add(3); myset.add(5); // Displays the properties and query the values of the hash set. Console.WriteLine(mySet.Count); Console.WriteLine(mySet.Contains(5)); Console.WriteLine(mySet.Contains(7)); 1 Fast adding, sorting and removing based on given values Li Haobin, ISEM Department,NUS 18

19 1.2 Standard Data Structure: Dictionary System Type System.Collections.Generic. Dictionary<Tkey,TValue> Description Represents a collection of keys and values. Dictionary Example: // Creates and initializes a new dictionary. Dictionary<string, string> mydict = new Dictionary<string, s t r i n g > ( ) ; mydict.add("1", "H"); mydict.add("3", "A"); mydict.add("5", "S"); // Displays the properties and query the values of the dictionary. Console.WriteLine(myDict.Count); Console.WriteLine(myDict.ContainsKey("5")); Console.WriteLine(myDict["3"]); Fast adding, sorting and removing based on given values H A D S 7 C 2017 Li Haobin, ISEM Department,NUS 19

20 1.2 Standard Data Structure: Tuple System Type System.Tuple Description Provides a static method of creating tuple objects. Tuple Example: // Create a 7 - tuple. var population = new T u p l e < s t r i n g, i n t, i n t, i n t, i n t, i n t, int> ( "New Y o r k ", , , , , , ); // Display the first and l a s t elements. Console.WriteLine("Population of 0 in 2000: 1:N0", p o pulation.item1, p o p u l a t i o n. I t e m 7 ) ; // The example d i s p l ays the f o l l o w i n g o u t p u t : // Population of New York in 2000: 8,008,278 Represents a data combination 2017 Li Haobin, ISEM Department,NUS 20

21 1.3 Input and Output Method Console Operation (Example) Console.Clear(); // prompt to key in the value of a Console.Write("Input: a = " ); double a = Convert.ToDouble(Console.ReadLine()); // prompt to key in the value of a Console.Write("Input: b = " ); double b = Convert.ToDouble(Console.ReadLine()); // prompt to press any key to continue Console.Write("Press any key to continue...") ; Console.ReadKey(); // Output the result Console.WriteLine("a + b = 0", a + b); 2017 Li Haobin, ISEM Department,NUS 21

22 1.3 Input and Output Method File Operations (Example) using System.IO; // Method to write to files using (StreamWriter sw = new StreamWriter(" f i l e. t x t " )) sw.writeline("hello W o r l d! " ) ; sw.writeline("welcome to C#!!"); // An easier method to read files foreach ( string line in F i l e. R e a d A l l L i n e s ( " f i l e. t x t " )) C o n s ole.writeline(line); // Method to read files by row using (StreamReader sr = new S t r e a m R e a d e r ( " f i l e. t x t " )) string line1 = sr.readline(); string line2 = sr.readline(); Console.WriteLine(line2); Console.WriteLine(line1); 2017 Li Haobin, ISEM Department,NUS 22

23 1.4 Loop Structure 4 different loops / / For loop f o r ( int i = 0; i < 10; i + + ) C o n s o l e. W r i t e L i n e ( i ) ; / / For Each loop / / While loop int i = 0 ; w h i l e ( i < 10) Consol e. Wr i t eli ne( i ); i++; / / Do-While loop int i = 0; do i n t [ ] arr = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ; foreach ( int i in arr) C o n s o l e. W r i t e L i n e ( i ) ; i++; C o n s o l e. W r i t e L i n e ( i ) ; while ( i < 10); 2017 Li Haobin, ISEM Department,NUS 23

24 1.4 Loop Structure Nested-Loop f o r ( int i = 0; i < 5; i + + ) for ( int j = 0; j < i ; j + + ) C o n s o l e. W r i t e L i n e ( " = 2", i, j, i + j); 2017 Li Haobin, ISEM Department,NUS 24

25 Practice One: Use loop structure to output the pattern below in the console * * * **** * * ** ****** *** *** *** ****** ***** ***** **** ****** ******* ******* ***** ****** ********* ***** ****** ****** *********** *** ******* ****** ************* * H i n t : M a t h. A b s ( x ) c a n b e u s e d t o c o m p u t e t h e a b s o l u t e v a l u e o f x Source code: Li Haobin, ISEM Department,NUS 25

26 1.5 Condition Structure // If condition int m = 12; i n t n = 18; if (m > 10) if (n > 20) Console.Wr iteline( "Result1 " ); else if (n > 15) Console.Wr iteline( "Result2 " ); else Console.WriteLine("Result3"); // Switch condition int caseswitch = 1; switch (caseswitch) case 1: Console.WriteLine("Case 1"); break; case 2: Console.WriteLine("Case 2"); break; case 3: Console.WriteLine("Case 3"); break; default: Console.WriteLine("Default c a s e " ); break; 2017 Li Haobin, ISEM Department,NUS 26

27 1.6 Function Method Realize the reuse of code Convenient for code management Differentiate between valuepassing and reference-passing Understand method overloading static void M a i n ( s t r i n g [] args) int a = 3, b = 4; Console.WriteLine( "0 1 2 ", Add(a, b ), a, b); Console.WriteLine( "0 1 2 ", Add(ref a, ref b ), a, b ) ; // Passing Values static int Add(int c, int d) c = c + 1; d = d + 2; return c + d; // Passing References static int Add(ref int c, r e f int d) c = c + 1; d = d + 2; return c + d; 2017 Li Haobin, ISEM Department,NUS 27

28 1.7 Lambda Expression A lambda expression is an anonymous function that you can use to create delegates or expression tree types. By using lambda expressions, you can write local functions that can be passed as arguments or returned as the value of function calls. A lambda expression is the most convenient way to create that delegate. int a = 3, b = 4; Func<int, i n t, int> func = c = c + 1; d = d + 2; return c + d; ( c, d) => ; //Func< int, int, int> func = (c, d) => c + d ; Console.WriteLine ("0 1 2 ", func(a, b), a, b ) ; //simple form 2017 Li Haobin, ISEM Department,NUS 28

29 1.8 LINQ Language-Integrated Query Language-Integrated Query i n t [] myints = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ; i n t [] arr1 = myints.select(x => x * x ). T o A r r a y ( ) ; // 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 i n t [] arr2 = myints.where(x => x > 5).ToArray(); // 6, 7, 8, 9, 10 i n t [] arr3 = myints.orderby(x => x % 3).ThenBy(x => x).toarray(); // 3, 6, 9, 1, 4, 7, 10, 2, 5, 8 i n t [] arr4 = myints.except(new i n t [] 3, 4, 5 ). T o A r r a y ( ) ; // 1, 2, 6, 7, 8, 9, 10 i n t [] arr5 = myints.concat(new i n t [] 10, 11, 12 ). T o A r r a y ( ) ; / /..., 6, 7, 8, 9, 10, 10, 11, 12 i n t [] arr6 = myints.take(6).toarray(); // 1, 2, 3, 4, 5, 6 i n t [] arr7 = Enumerable.Range(1, 1 0 ). T o A r r a y ( ) ; // 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 i n t [] arr8 = Enumerable.Repeat(1, 1 0 ). T o A r r a y ( ) ; // 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 i n t [] arr9 = arr5.distinct().toarray(); // 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, Li Haobin, ISEM Department,NUS 29

30 1.8 LINQ Language-Integrated Query Language-Integrated Query int agg1 = myints.max(); // 10 int agg2 = myints.min(); // 1 int agg3 = myints.sum(); // 55 double agg4 = myints.average(); // 5.5 int agg5 = myints.aggregate(1, ( i, j) => i * 2 + j ) ; // 3060 int agg6 = m y I n t s. F i r s t ( ) ; / / F i r s t O r D e f a u l t ( ) ; // 1 int agg7 = m y I n t s. L a s t ( ) ; / / L a s t O r D e f a u l t ( ) ; // Li Haobin, ISEM Department,NUS 30

31 Object-oriented Programming (OOP) 2017 Li Haobin, ISEM Department,NUS 31

32 1.9 Encapsulation Encapsulation describes the idea of grouping data and associated functionalities into a single package and hiding internal details from outsider. The two terms Class and Object are sometimes interchangeable in use; however, class is the type of the described object while object is the available instance of a class. As such, the operation of creating objects is called instantiation Li Haobin, ISEM Department,NUS 32

33 1.9 Encapsulation Properties and Fields Properties and fields: describes the information contained in the object Fields are similar to variables, as it can be accessed or set up directly Properties can be get or set, and provide more control on setting and returning values p u b l i c class SampleClass p r i v a t e i n t _sample; p u b l i c i n t Sample // Return the value stored in a field. get return _sample; // Store the value in the field. s e t _sample = v a l u e ; public class SampleClass p u b l i c i n t Sample g e t ; set; 2017 Li Haobin, ISEM Department,NUS 33

34 1.9 Encapsulation - Methods Methods are possible operations to be made on objects For the same method, there can be various implementations for a class, this is also called override ; the difference between implementations is due to difference in number of parameters and parameter types. public class SampleClass public int SampleProperty get; set; public i n t SampleMethod(string sampleparam) return sampleparam.length; public i n t SampleMethod(int sampleparam) r e t u r n sampleparam + 1; 2017 Li Haobin, ISEM Department,NUS 34

35 1.9 Encapsulation Modifier All classes and class methods can use modifiers to provide different level of accessibilities. These are the different modifiers: C# modifier Definition (Who can access) public private protected internal protected internal private protected Any code. No inheritance, external type, or external assembly restrictions Only members within the same type. (default for type members) Only derived types or members of the same type Only code within the same assembly. Can also be code external to object as long as it is in the same assembly. (default for types) Either code from derived type or code in the same assembly. Combination of protected or internal The containing class or types derived from the containing class within the current assembly 2017 Li Haobin, ISEM Department,NUS 35

36 1.9 Encapsulation -- Constructor A constructor is a method that is called when you create an object and it usually initializes the data members of the new object. Constructor is only called when you create an object. The code of a constructor will always run before other code in the same class. However, more constructor overwriting can be created by using the same overriding method. p u b l i c class SampleClass public SampleClass() // Add code here 2017 Li Haobin, ISEM Department,NUS 36

37 1.9 Encapsulation Instantiable Class Instantiable class is needed to create objects, that is, to create class instantiation. SampleClass sampleobject = new SampleClass(); // Set a property v a l u e. sampleobject.sampleproperty = "Sample S t r i n g " ; // Call a method. sampleobject.samplemethod(30); // Set a property value w i t h c o n s t r u c t i o n. SampleClass sampleobject = new SampleClass() SampleProperty = "Sample S t r i n g " ; // Call a method. sampleobject.samplemethod(30); 2017 Li Haobin, ISEM Department,NUS 37

38 1.9 Encapsulation Nested Class A class defined in another class is called nested class public class Container public class Nested // Add code h ere. // Instantiate nested class Container.Nested nestedinstance = new Container.Nested(); 2017 Li Haobin, ISEM Department,NUS 38

39 1.9 Encapsulation Static Class and Members Static members of a class is the properties, processes and fields shared by all the instantiations in the class. A static class can contain only static members and it cannot be instantiated. Static members cannot access properties, fields or methods that are not static. // define static members: static class SampleClass public static s t r i n g SampleString = "Sample S t r i n g " ; // Use the name of the class to access static members, but do not create objects of the class. Console.WriteLine(SampleClass.SampleString); 2017 Li Haobin, ISEM Department,NUS 39

40 1.9 Encapsulation The Realization of Entity Relationship Use class to define how two entities are related to each other. class Location // Define Location class public i n t I d get; set; public double Capacity get; set; public List<SKU> SKUs get; set; = new List<SKU>(); / / describe relationship with SKU public double Occupation get return SKUs.Sum(sku => sku.size); class SKU / / define SKU class public i n t I d get; private set; public double Size get; private set; public List<Location> Storage get; p rivate set; = new List<Location>(); // describe relationship with Location public SKU(int id, double s i z e, Location[] storage) //Two-way references are realized through the use of constructor Id = id; Size = s i z e ; Storage = storage.tolist(); foreach (Location loc in storage) loc.skus.add(this); 2017 Li Haobin, ISEM Department,NUS 40

41 1.9 Encapsulation The Realization of Entity Relationship Use class to define how two entities relate to each other. // Instantiation of Locations List<Location> locs = new List<Location> ; new Location Id = 0, Capacity = 15, new Location Id = 1, Capacity = 15, new Location Id = 2, Capacity = 20, new Location Id = 3, Capacity = 20, new Location Id = 4, Capacity = 20 // Add information of SKU, List<SKU> skus = new List<SKU>(); skus.add(new SKU(0, 0.8, new Location[] locs[0], locs[0], locs[0], l o c s [ 1 ] ) ) ; skus.add(new SKU(1, 0.5, new Location[] locs[1], locs[2], locs[3], l o c s [ 4 ] ) ) ; skus.add(new SKU(2, 1. 2, new L o c a t i o n [ ] l o c s [ 1 ], l o c s [ 2 ], l o c s [ 2 ], l o c s [ 4 ], l o c s [ 4 ] )); skus.add(new SKU(3, 1.5, new Location[] l o c s [ 3 ], l o c s [ 3 ], l o c s [ 3 ] ) ) ; 2017 Li Haobin, ISEM Department,NUS 41

42 Practice Two: Take the Location-SKU entity relationship instantiation above as example, use LINQ to answer the questions below: Which are the SKUs whose storage use more than 3 spaces? Which are the SKUs whose storage use more than 4 spaces? Order the location of SKUs according to spare space. Which are the locations with 3 SKUs being stored? Thinking: How to adjust the storage such that The stock volume is distributed to every location as even as possible? The spare volume is maximum for single location? Source code: Li Haobin, ISEM Department,NUS 42

43 1.10 Inheritance Inheritance is one of the basic features of OOP, with the ability to create a class that inherits, develops or modifies properties and behaviors from an existing class. The newly created class is the derived (or child) class and the existing class is the base (or parent) class. p u b l i c class A p u b l i c i n t Value1() r e t u r n 10; p u b l i c class B : A p u b l i c i n t Value2() r e t u r n 20; p u b l i c class C : B p u b l i c int Value3() r e t u r n 30; // Instantiation A a = new A(); B b = new B(); C c = new C(); Console.WriteLine( "0", a. V a l u e 1 ( ) ) ; Console.WriteLine("0 1 ", b. V a lue1(), b. V a l u e 2 ( ) ) ; Console.WriteLine("0 1 2 ", c. Value1 (), c. Value2 ( ), c. V a l u e 3 ( ) ) ; 2017 Li Haobin, ISEM Department,NUS 43

44 1.11 Polymorphism Base class can define and realize the virtual methods while the derived class can override the methods by providing its own definitions and implementations. Virtual method provides a uniform method to implement several related objects. p u b l i c class A p u b l i c v i r t u a l int Value1() r e t u r n 10; p u b l i c class B : A p u b l i c override i n t Value1() r e t u r n 11; p u b l i c i n t Value2() r e t u r n 20; p u b l i c class C : B p u b l i c override i n t Value1() r e t u r n 12; p u b l i c i n t Value3() r e t u r n 30; // Instantiation A a = new A(); B b = new B(); C c = new C(); Console.WriteLine( "0", a. V a l u e 1 ( ) ) ; Console.WriteLine("0 1 ", b. V a lue1(), b. V a l u e 2 ( ) ) ; Console.WriteLine("0 1 2 ", c. Value1 (), c. Value2 ( ), c. V a l u e 3 ( ) ) ; 2017 Li Haobin, ISEM Department,NUS 44

45 1.12 Interface An interface in C# contains the declaration of the methods, properties, and events of the class. For example, the use of interface in a class may contain behaviors from multiple sources. This feature is important in C# as C# does not support multiple inheritance. interface IEquatable<T> bool Equals(T o b j ) ; p u b l i c class Car : IEquatable<Car> p u b l i c string Make g e t ; s e t ; p u b l i c s t r i n g Model g e t ; set; p u b l i c string Year g e t ; s e t ; // Implementation of IEquatable<T> i n t e r f a c e p u b l i c bool Equals(Car c a r ) if (this.make == car.make && this.model == car.model && this.year == car.year) return true; else r e t u r n f a l s e ; 2017 Li Haobin, ISEM Department,NUS 45

46 1.13 Example: 24 Point Intellectual Program Given 4 numbers randomly, get the result of 24 by arithmetic operation Finite solution set, searching is not difficult The key is how to define, test and traverse operation expressions (system configuration) 2017 Li Haobin, ISEM Department,NUS 46

47 1.13 Example: 24 Point Intellectual Program Step 1:define the class p u b l i c class Expr p u b l i c Expr Operand1 g e t ; s e t ; p u b l i c Expr Operand2 get; set; p u b l i c string Operator get; set; p r i v a t e double? _value; // public double Value g e t ; s e t ; // see next page p u b l i c override string ToString() if (_value is null) r e t u r n s t r i n g. F o r m a t ( " ( ) ", Operand1, Operator, Operand2); r e t u r n _ value.value.tostring(); 2017 Li Haobin, ISEM Department,NUS 47

48 1.13 Example: 24 Point Intellectual Program //... p u b l i c double Value set _value = value; // assign value get // get value double value = 0 ; if (_value is null) switch (Operator) case "+": value = Operand1.Value + Operand2.Value; br e ak; case " - " : value = Operand1.Value - Operand2.Value; break; case "*": value = Operand1.Value * Operand2.Value; br e ak; case "/": value = Operand1.Value / Operand2.Value; b reak; if (value < 0) return double.nan; r e t u r n value; r e t u r n _value.value; Step 2:Calculation Class 2017 Li Haobin, ISEM Department,NUS 48

49 Practice 3(A): Use the previous Expr Class, construct and test the following expressions ( ) x 12 8 / x 10 Source code: Li Haobin, ISEM Department,NUS 49

50 1.13 Example: 24 Point Intellectual Program Step 3: traverse all operation expressions // Given the set of operands, return all possible expressions static List<Expr> GetExpr(int[] arr) // Initialize the return value var exprs = new List<Expr>(); // Separate the numbers into two parts of left and right var divs = new L i s t < T u p l e < i n t [ ], int[]>>(); 2017 Li Haobin, ISEM Department,NUS 50

51 1.13 Example: 24 Point Intellectual Program // Search for all possible ways of separating into two parts, store the results in divs s w i t c h ( a r r. L e n g t h ) c a s e 1 : r e t u r n n e w L i s t < E x p r > n e w E x p r V a l u e = a r r [ 0 ] ; // R e t u r n e x p r e s s i o n d i r e c t l y i f t h e r e i s o n l y o n e o p e r a n d c a s e 2 : d i v s = n e w L i s t < T u p l e < i n t [ ], i n t [ ] > > n e w T u p l e < i n t [ ], i n t [ ] > ( n e w i n t [ ] a r r [ 0 ], n e w i n t [ ] a r r [ 1 ] ) ; b r e a k ; c a s e 3 : d i v s = n e w L i s t < T u p l e < i n t [ ], i n t [ ] > > n e w T u p l e < i n t [ ], i n t [ ] > ( n e w i n t [ ] a r r [ 0 ], n e w i n t [ ] a r r [ 1 ], a r r [ 2 ] ), n e w T u p l e < i n t [ ], i n t [ ] > ( n e w i n t [ ] a r r [ 1 ], n e w i n t [ ] a r r [ 0 ], a r r [ 2 ] ), n e w T u p l e < i n t [ ], i n t [ ] > ( n e w i n t [ ] a r r [ 2 ], n e w i n t [ ] a r r [ 0 ], a r r [ 1 ] ), ; b r e a k ; c a s e 4 : divs = n e w L i s t < T u p l e < i n t [ ], int[ ] > > new T u p l e < int[ ], i nt[]>(new int[] arr[0], new int[] arr[1], arr[ 2 ], arr[3] ), new T u p l e < int[ ], i nt[]>(new int[] arr[1], new int[] arr[0], arr[ 2 ], arr[3] ), new T u p l e < int[ ], i nt[]>(new int[] arr[2], new int[] arr[0], arr[ 1 ], arr[3] ), new T u p l e < int[ ], i nt[]>(new int[] arr[3], new int[] arr[0], arr[ 1 ], arr[2] ), new T u p l e < int[ ], int[]>(new i n t [] arr[ 0 ], arr[1], new int[] arr[ 2 ], arr[3] ), new T u p l e < int[ ], int[]>(new int[ ] arr[0], arr[2], new i n t [ ] arr[ 1 ], arr[3] ), new T u p l e < int[ ], int[]>(new int[ ] arr[0], arr[3], new i n t [ ] arr[ 1 ], arr[2] ), ; break; 2017 Li Haobin, ISEM Department,NUS 51

52 1.13 Example: 24 Point Intellectual Program // For each result of two-part separation, use recursion to generate two expression pairs of left and right. var pairs = d i v s. S e l e c t ( t => new Tuple<List<Expr>, List<Expr>>(GetExpr(t.Item1), G e t E x p r ( t. I t e m 2 ) ) ). T o L i s t ( ) ; // Transverse all pairs foreach (Tuple<List<Expr>, List<Expr>> pair in pairs) foreach (Expr exp1 i n pair.item1) foreach (Expr exp2 in pair.item2) // Transverse operators to generate expressions. exprs.add(new Expr Operand1 = exp1, Operand2 = exp2, Operator = "+" ); exprs.add(new Expr Operand1 = exp1, Operand2 = exp2, Operator = "*" ); exprs.add(new Expr Operand1 = exp1, Operand2 = exp2, Operator = " - " ); exprs.add(new Expr Operand1 = exp2, Operand2 = exp1, Operator = " - " ); exprs.add(new Expr Operand1 = exp1, Operand2 = exp2, Operator = "/" ); exprs.add(new Expr Operand1 = exp2, Operand2 = exp1, Operator = "/" ); // Return the results r e t u r n exprs; 2017 Li Haobin, ISEM Department,NUS 52

53 Practice 3(B): Answer without using the above code: How many expression combinations are there given any 1 random number? How many expression combinations are there given any 2 random numbers? Answer by using the above code: How many expression combinations are there given any 3 random numbers? How many expression combinations are there given any 4 random numbers? Thinking question: How many expression combinations are there given any 4 random numbers? Source code: Li Haobin, ISEM Department,NUS 53

54 1.13 Example: 24 Point Intellectual Program Step 4: Searching ( A trivial case) while ( true) Console.WriteLine("==== GET 24 ===="); var exprs = GetExpr(Console.ReadLine().Split( ' ' ). S e l e c t ( s => Convert.ToInt32(s)).Take(4).ToArray()); foreach ( v a r expr in exprs) if (expr.value == 24) Console.WriteLine(expr); Console.WriteLine(); 2017 Li Haobin, ISEM Department,NUS 54

55 Practice 3(C): Question: Why is the game designed to calculate 24 instead of any other umbers (write a numerical experiment program to answer)? Is it possible to design a game that make calculations using 3 numbers only? Source code: Li Haobin, ISEM Department,NUS 55

56 Practice 3(C): No. of possible combinations Average no. of possible expressions Li Haobin, ISEM Department,NUS 56

57 Thank You! 2017 Li Haobin, ISEM Department,NUS 57