\n C++ Programming Course<\/a>\n <\/p>\n Master key C++ programming concepts like variables, functions, OOP, and control structures. Build real-world projects such as a banking system and grade management tool.<\/p>\n So, this blog is here to help you out in understanding the details of templates in c++, how they work, templates specialization, templates library and many more. Read on to know more!<\/p>\n\n\n\n Templates in C++ is an interesting feature that is used for generic programming and templates in c++ is defined as a blueprint or formula for creating a generic class or a function. Simply put, you can create a single function or single class to work with different data types using templates. <\/p>\n\n\n\n C++ template is also known as generic functions or classes which is a very powerful feature in C++. A keyword \u201ctemplate\u201d in c++ is used for the template\u2019s syntax and angled bracket in a parameter (t), which defines the data type variable.<\/p>\n\n\n\n Templates in c++ works in such a way that it gets expanded at compiler time, just like macros and allows a function or class to work on different data types without being rewritten.<\/p>\n\n\n\n There are two types of templates in C++<\/p>\n\n\n\n A function template in c++ is a single function template that works with multiple data types simultaneously, but a standard function works only with one set of data types.<\/p>\n\n\n\n Here, type is a placeholder name for a data type used by the function. It is used within the function definition.<\/p>\n\n\n\n The class keyword is used to specify a generic type in a template declaration.<\/p>\n\n\n\n C++ function template example:<\/strong><\/p>\n\n\n\n Source Code:<\/strong><\/p>\n\n\n\n Defining a Class Member Outside the Class Template<\/strong><\/p>\n\n\n\n You\u2019ve seen how a member function is defined within a class template. Now, alternatively, it is also possible for the template member function to be defined independently of the declaration of its class template.<\/p>\n\n\n\n The compiler will use the template arguments that you used, in this case, to create the class template when you call a member function of a class template specialization. The following illustration exemplifies this:<\/p>\n\n\n\n Example:<\/em><\/strong><\/p>\n\n\n\n A definition of the overloaded addition operator is given outside of class A. It is equal to the statement ob1.operator+('p') rather than ob1+ \"p\". \"ob2 + 10\" is similar to \"ob2.operator+\" (10).<\/p>\n\n\n\n Simple Calculator Using Class Templates<\/strong><\/p>\n\n\n\n We can make a simple Calculator performing the four basic arithmetic operations in C++ using a class template. The template of the class will consist of two variables whose values are passed at the time of object creation. The constructor of this class takes two arguments of generic datatypes. Further, you will see, this Calculator class template consists of five main functions \u2013 show(), addition(), subtraction(), multiplication(), and division(). The show() function is responsible for calling the rest of the four generic functions. Moving ahead, we have created two instances from the template of Calculator class and performed the basic calculations using its class functions. <\/p>\n\n\n\n Example:<\/strong><\/p>\n\n\n\n Output <\/p>\n\n\n\n C++ Class Templates With Multiple Parameters<\/strong><\/p>\n\n\n\n It is possible to provide more than one type when generating templates. A class template can have many generic data types. They are listed in a comma-delimited format as shown in the following example.<\/p>\n\n\n\n Example:<\/em><\/strong><\/p>\n\n\n\n Output:<\/em><\/strong><\/p>\n\n\n\n As seen in the above cited example, we can use more than one parameter for a template in C++. Here, the template Temp takes two parameters, both of the Sample class type, separated by a comma. Moreover, the constructor of the Sample class takes two arguments of generic datatype. When we create objects, the types of arguments are specified in angular brackets (< >). In case of multiple parameters, the datatypes are also separated by commas. The constructor is called at the time when objects are created, and template arguments receive values.<\/p>\n\n\n\n The class template in c++ is like function templates. They are known as generic templates. They define a family of classes in C++. <\/p>\n\n\n\n Syntax of Class Template<\/strong> <\/p>\n\n\n Here Type is a placeholder type name, which will be specified when a class instantiated.<\/p>\n\n\n\n The Type can be used inside the body of the class. <\/p>\n\n\n\n Class template in c++ example:<\/strong><\/p>\n\n\n\n Source Code:<\/strong><\/p>\n\n\n\n Templates Specialization is defined as a mechanism that allows any programmer to use types as parameters for a class or a function. A function\/class defined using the template is called a generic function\/class, and the ability to use and create generic functions\/classes is one of the critical features of C++.<\/p>\n\n\n\n <\/p>\n\n\n\n We have the add() function, which takes two parameters and returns the same type of data after adding the two args.<\/p>\n\n\n\n Function specialization<\/strong> example: <\/strong><\/p>\n\n\n\n Source Code:<\/strong><\/p>\n\n\n\n Class specialization<\/strong> example: <\/strong><\/p>\n\n\n\n Source Code:<\/strong><\/p>\n\n\n\n When we write any template-based function or class, the compiler creates a copy of that function\/class whenever the compiler sees that being used for a new data type or a new set of data types(in case of multiple template arguments). Template parameters can be types, non-types, and templates.<\/p>\n\n\n\n Integrals are the most used non-types. std::array is the typical example because you have to specify at compile time the size of a std::array:<\/p>\n\n\n\n Std::array<int, 3> myarray{1, 2, 3};<\/p>\n\n\n\n The non-type parameters can be passed to templates. They mainly focus on passing the constant expression i.e address of a function, object or static class member at compile time. Non-type parameters are also used for specifying max or min values for a particular instance of a template.<\/p>\n\n\n\n Item templates may only specify one item, but sometimes the item is made up of multiple files.<\/p>\n\n\n\n The set of parameters spans all files of a multi-file template. If you use the same parameter $PARAM$ in several files of a multi-file template, it will have the same value in all related files when the template is applied.<\/p>\n\n\n\n If a multi-file template has editable parameters, the Hot Spot Session, which deploys when you apply this template, will guide you through all created files where the user input is required.<\/p>\n\n\n\n Multi-file item template example:<\/strong><\/p>\n\n\n The files that you have selected are compressed into a .zip file.<\/p>\n\n\n\n <Version>TemplatesItemTemplates' by default.<\/p>\n\n\n\n The multi-file item template appears in the 'Add New Item'<\/strong> dialogue box.<\/p>\n\n\n\n A standard template library in C++ is a repository of C++ template classes. These template classes help in implementing commonly used algorithms and data structures. These template classes can be used with any user-defined type as well as a built-in type. STL algorithms are container-independent and thus reduce the complexity of the library. This approach implements compile-time polymorphism over run-time polymorphism. <\/p>\n\n\n\n This brings us to the end of the blog on Templates in C++. Hope this helps you to up-skill your C++ skills. To learn more about programming and other related concepts, check out the courses on Great Learning Academy<\/a>. <\/p>\n\n\n\nTable of Contents <\/strong><\/h3>\n\n\n\n
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What is Templates in C++?<\/strong><\/h2>\n\n\n\n
How do templates work in C++?<\/strong><\/h2>\n\n\n\n
Types of Templates in C++<\/strong><\/h2>\n\n\n\n
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![\"Types](\"https:\/\/www.mygreatlearning.com\/blog\/wp-content\/uploads\/2022\/09\/image-8-1024x337.png\")
<\/figure>\n\n\n\nWhat is the function template in C++?<\/strong><\/h2>\n\n\n\n
C++ Function Template Syntax<\/strong><\/h4>\n\n\n
\ntemplate<class type>ret-type func-name(parameter list)\n{\n\/\/body of the function\n}\n<\/pre><\/div>\n\n\n#include<iostream.h>\nusing namespace std;\ntemplate<classX>\/\/can replace 'class\" keyword by \"typename\" keyword\nX func( Xa,Xb)\n{\nreturn a;\n}\nint main()\ncount<<func(15,8),,endl;\/\/func(int,int);\ncount,,func('p','q'),,endl;\/\/func(char,char);\ncount<<func(7.5,9.2),,endl;\/\/func(double,double)\nreturn();\n}\n<\/code><\/pre>\n\n\n\nOutput \n15\np\n7.5<\/code><\/pre>\n\n\n\n#include<iostream>\nusing namespace std;\n template<class A> class B {\n public:\n A operator+(A);\n};\n\ntemplate<class A> A B<A>::operator+(A x) {\n return x;\n};\n\nint main() {\n B<char> ob1;\n B<int> ob2;\n cout<< ob1 +'p' << endl;\n cout<< ob2 + 10;\n return 0;\n}\n<\/code><\/pre>\n\n\n\nOutput:\nP\n10<\/code><\/pre>\n\n\n\ntemplate <class Temp>\nclass Calculator\n{\nprivate:\n Temp n1, n2;\n \npublic:\n Calculator(Temp num1, Temp num2)\n {\n n1 = num1;\n n2 = num2;\n }\n \n void show()\n {\n cout << \"Addition is: \" << n1 << \"+\" << n2 << \"=\" << addition() << endl;\n cout << \"Subtraction is: \" <<n1 << \"-\" << n2 << \"=\" << subtraction() << endl;\n cout << \"Product is: \" << n1 << \"*\" << n2 << \"=\" << multiplication() << endl;\n cout << \"Division is: \" << n1 << \"\/\" << n2 << \"=\" << division() << endl;\n }\n \n Temp addition() { return (n1 + n2); }\n \n Temp subtraction() { return n1 - n2; }\n \n Temp multiplication() { return n1 * n2; }\n \n Temp division() { return n1 \/ n2; }\n};\n\nint main()\n{\n Calculator<int> Calc1(25, 12);\n Calculator<float> Calc2(13.6, 5.9);\n \n cout << \"Integer results for 25 and 12:\" << endl;\n Calc1.show();\n \n cout << endl << \"Float results for 13.6 and 5.9:\" << endl;\n Calc2.show();\n \n return 0;\n}\n<\/code><\/pre>\n\n\n\n![](\"https:\/\/lh5.googleusercontent.com\/Q6di86R-9-Tm647UPDfio4bxa9uZ4Zo77MMcWJfO2hT4u-mK-Hro3o9Jw19c2pXnbWK0QZjEVQPsd_D3FxvJO5Zht4KmOoMdq2p80JB26WrYhM7Td4pMiYgW1deaAlUT3kCnBwMcrmwVHSichrBjXcz6liKy3iwSTMsMtvPPbqjOYOXcCU3Mn2lu45l2gOiEfAGPKw\")
#include<iostream>\nusing namespace std;\n\n\/\/ Class template with more than one parameter\ntemplate<class Temp1, class Temp2>\nclass Sample\n{\n\t\tTemp1 l;\n\t\tTemp2 m;\n\tpublic:\n\t\tSample(Temp1 a, Temp2 b)\n\t\t{\n\t\t\tl = a;\n\t\t\tm = b;\n\t\t}\n\t\tvoid display()\n\t\t{\n\t\t\tcout << \"The inputs are: \" <<l << \" and \" << m << endl;\n\t\t}\n};\n\n\/\/ Driver function\nint main()\n{\n\t\/\/ instantiation\n\tSample <int, char> ob1 (24, 'A');\n\t\n\t\/\/ instantiation \n\tSample<int, float> ob2(22.56, 34.9);\n\t\n\t\/\/Calling the display function to see the output\n ob1.display();\n\tob2.display();\n\t\n\treturn 0;\n}\n<\/code><\/pre>\n\n\n\n
<\/figcaption><\/figure>\n\n\n\nWhat is class template in c++<\/strong>?<\/h2>\n\n\n\n
\ntemplate<class Ttype>\nclass class_name\n{\n\/\/class body;\n}\n<\/pre><\/div>\n\n\n#include<iostream.h>\nusing namespace std;\ntemplate <class C>\nclass A{\nprivate;\nC,a,b;\npublic:\nA(Cx,Cy){\na=x;\nb=y;\n}\nvoid show()\n}\ncount<<\"The Addition of\"<<a<<\"and\"<<b<<\"is\"<<add()<<endl;\n}\nC add(){\nC c=a+b;\nreturn c;\n}\n};\nint main(){\nAaddint(8,6);\nAaddfloat(3.5,2.6);\nAaaddouble(2.156,5.234);\nAaddint.show();\ncout<<endl;\nadddouble.show();\ncount<<endl;\nreturn 0;\n}\n\n<\/code><\/pre>\n\n\n\nOutput\nThe addition of 8 and 6 is 14 \nAddition of 3.5 and 2.6 is 6.1\nThe addition of 2.156 and 5.234 is 7.390<\/code><\/pre>\n\n\n\nDifference between function overloading and templates in C++?<\/strong><\/h2>\n\n\n\n
Function overloading<\/strong><\/td> Function Template<\/strong><\/td><\/tr> This is used when multiple functions do similar operations.<\/td> This is used when functions do identical operations.<\/td><\/tr> Function overloading<\/a> can take varying numbers of arguments.<\/td> Templates cannot take varying numbers of arguments.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Advantages of Using Templates in C++<\/strong><\/h2>\n\n\n\n
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Disadvantages of Using Templates in C++<\/strong><\/h2>\n\n\n\n
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Overloading of C++ template<\/strong><\/h2>\n\n\n\n
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What is Templates Specialization? <\/strong><\/h2>\n\n\n\n
\/\/A generic sort function\ntemplate<class X>\n{\n\/\/code to implement quick sort\n}\n\/\/Template specilization:A function\n\/\/specialized for char data type\ntemplate<>\nvoid sort<char>(char arr[],int size)\n{\n\/\/code to impletement counting sort\n}<\/code><\/pre>\n\n\n\nFunction Specialization<\/strong><\/h2>\n\n\n\n
#include <iostream.h>\nusing namespace std ;\n\n\/\/max returns the maximum of the two elements of type T, where T is a\n\/\/class or data type for which operator> is defined.\ntemplate <class T>\nT max(T a, T b)\n{\n return a > b ? a : b ;\n}\n\nint main()\n{ \n cout << \"max(80, 95) = \" << max(10, 15) << endl ;\n cout << \"max('a', 'z') = \" << max('k', 's') << endl ;\n cout << \"max(11.1, 18.2) = \" << max(11.1, 18.2) << endl ;\n cout << \"max(\"Ahil\", \"Riya\") = \" << max(\"Ahil\", \"Riya\") << endl ;\n return 0 ;\n}\n<\/code><\/pre>\n\n\n\nOutput\nmax(80, 95) = 95\nmax('a', 'z') = z\nmax(11.1, 18.2) = 18.2\nmax(\"Ahil\", \"Riya\") = Riya\n<\/code><\/pre>\n\n\n\n Class Specialization<\/strong><\/h2>\n\n\n\n
#include <iostream> \nusing namespace std; \n \ntemplate <class T> \nclass Test \n{ \n \/\/ Data memnbers of test \npublic: \n Test() \n { \n \/\/ Initialization of data members \n cout << \"General template n\"; \n } \n \/\/ Other methods of Test \n}; \n \ntemplate <> \nclass Test <int> \n{ \npublic: \n Test() \n { \n \/\/ Initialization of data members \n cout << \"Specialized template n\"; \n } \n}; \n \nint main() \n{ \n Test<int> a; \n Test<char> b; \n Test<float> c; \n return 0; \n} <\/code><\/pre>\n\n\n\nOutput\nSpecialized template \nGeneral template \nGeneral template \n<\/code><\/pre>\n\n\n\nHow does template specialisation work?<\/strong><\/h2>\n\n\n\n
If a specialised version is present, the compiler first checks with the specialised version and then the main template. The compiler first checks with the most specialised version by matching the passed parameter with the data type(s) specified in a specialised version.<\/p>\n\n\n\nTemplate Parameter<\/strong><\/h2>\n\n\n\n
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Can we pass non-type parameters to templates?<\/strong><\/h2>\n\n\n\n
Source Code<\/strong><\/h4>\n\n\n\n
template <std::string * temp> \/\/pointer to object\nvoid f()\n{\n cout << *temp << endl;\n}\n\ntemplate <std::string & temp> \/\/reference to object\nvoid g()\n{\n cout << temp << endl;\n temp += \"...appended some string\";\n}\n\nstd::string s; \/\/must not be local as it must have external linkage!\n\nint main() {\n s = \"can assign values locally\";\n f<&s>();\n g<s>();\n cout << s << endl;\n return 0;\n}<\/code><\/pre>\n\n\n\nOutput:<\/strong><\/h4>\n\n\n\n
Output\n<\/strong>Can assign values locally\nAssign values locally\nWe can assign values locally...appended some string\n<\/code><\/pre>\n\n\n\nCreate Multi-File Templates<\/strong><\/h2>\n\n\n\n
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Manually create a multi-file item template.<\/strong><\/h4>\n\n\n\n
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\n<ProjectItem TargetFileName="$fileinputname$.vb">\n Form1.vb\n<\/ProjectItem>\n<ProjectItem TargetFileName="$fileinputname$.Designer.vb">\n Form1.Designer.vb\n<\/ProjectItem>\n<ProjectItem TargetFileName="$fileinputname$.resx">\n Form1.resx\n<\/ProjectItem>\n<\/pre><\/div>\n\n\n
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Example<\/strong><\/h4>\n\n\n\n
<VSTemplate Version=\"2.0.0\" Type=\"Item\"\n xmlns=\"http:\/\/schemas.microsoft.com\/developer\/vstemplate\/2005\">\n <TemplateData>\n <Name>Multi-file Item Template<\/Name>\n <Icon>Icon.ico<\/Icon>\n <Description>An example of a multi-file item template<\/Description>\n <ProjectType>VisualBasic<\/ProjectType>\n <\/TemplateData>\n <TemplateContent>\n <ProjectItem TargetFileName=\"$fileinputname$.vb\" SubType=\"Form\">\n Form1.vb\n <\/ProjectItem>\n <ProjectItem TargetFileName=\"$fileinputname$.Designer.vb\">\n Form1.Designer.vb\n <\/ProjectItem>\n <ProjectItem TargetFileName=\"$fileinputname$.resx\">\n Form1.resx\n <\/ProjectItem>\n <\/TemplateContent>\n<\/VSTemplate><\/code><\/pre>\n\n\n\nStandard Template Library in C++<\/strong><\/h2>\n\n\n\n
![\"\"\/](\"https:\/\/lh4.googleusercontent.com\/KZUbf4HO4px5am34ew_2-f6THDGqlK5GtwrR4yaX4Mqalzlh1BqsiqHK-NGRDRFLyGLqsUB8hYA4zSb-_BneQqFCgE5ws5tQByVSfQ7gvzklrQZkQnNVISsiN80mLFjldVuVwsZF5iBE0R7gKDC7td67KdZwwt7KcMExOc9Y4WTry1kSHU_qi4ai1A70Tl_SItGWfA\")