Variadic function templates in C++
Syntax for a variadic function template: :
template(typename arg, typename... args) return_type function_name(arg var1, args... var2) Note :, typename arg, typename... args must be inside angular brackets.
Below is an example in C++ to show how we can use variadic function template:
1 2 3.14 Pass me any number of arguments I will print I am empty function and I am called at last.
Remember that templates are replaced by actual functions by compiler.
The variadic templates work as follows :
The statement, print(1, 2, 3.14, “Pass me any number of arguments”, “I will print\n”); is evaluated in following manner :
Firstly, the compiler resolves the statement into
cout<< 1 <<endl ; print(2, 3.14, "Pass me any number of arguments", "I will print\n");
Now, the compiler finds a print() function which can take those arguments and in result executes the variadic print() function again in similar manner :
cout<< 2 <<endl ; print(3.14, "Pass me any number of arguments", "I will print\n");
Again, it is resolved into the following forms :
cout<< 3.14 <<endl ; print("Pass me any number of arguments", "I will print\n");
cout<< "Pass me any number of arguments" <<endl ; print("I will print\n");
cout<< "I will print\n" <<endl ; print();
Now, at this point the compiler searches for a function overload whose match is the empty function i.e. the function which has no argument.
This means that, all functions that have 1 or more arguments are matched to the variadic template and all functions that with no argument are matched to the empty function.
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