C++ using vs Typedef

Last Updated : 17 Dec, 2022

typedef keyword in C++ is used for aliasing existing data types, user-defined data types, and pointers to a more meaningful name. Typedefs allow you to give descriptive names to standard data types, which can also help you self-document your code. Mostly typedefs are used for aliasing, only if the predefined name is too long or complex to write again and again. The unnecessary use of typedef is generally not a good practice.

Syntax:

typedef <current_name> <new_name>

Example:

typedef std::vector<int> vInt;

Using in C++ STL

The using keyword in C++ is used to bring a specific member or all members into the current scope and bring base class variables/methods into the derived class’s scope.

Syntax:

using <member_name>

Example:

using std::cout;

Typedef Vs Using In C++ STL

Typedef in C++ STL	Using in C++ STL
Typedef cannot be used with a template.	Using can be used with a template.
It requires the type name.	It does not require the type name.
It is difficult to modify.	It is comparatively easy to modify.
It is not much readable.	It is comparatively readable.
Typedef is an init-statement.	Using is not an init-statement
The Pointer declaration is not much clean.	The Pointer declaration is comparatively clean.
Syntax: typedef struct struct_type short_type_t;	Syntax: template<[template-parameters (T1, …)]> using [alias] = [original-type];
Creating a generic alias: template<typename T> struct Salary { typedef std::map<Employee_id, std::vector<T>> type; }; Salary<Employee_Salary>::type Employee_Salary;	Creating a generic alias: template<typename T> using Salary = std::unordered_map<Employee_id, std::vector<T>>;

Example:

C++

// C++ Program to implement typedef 
#include <bits/stdc++.h> 
    
using namespace std; 
    
int main() 
{ 
    // Now we can make more vectors by using vInt 
    typedef std::vector<int> vInt; 
    
    // vec1 is a vectorof type int 
    vInt v; 
    
    v.push_back(190); 
    v.push_back(180); 
    v.push_back(10); 
    v.push_back(10); 
    v.push_back(27); 
    
    for (auto X : v) { 
        cout << X << " "; 
    } 
    
    return 0; 
}

Output

190 180 10 10 27

Example:

C++

// C++ Program to implement using 
#include <bits/stdc++.h> 
    
using namespace std; 
    
int main() 
{ 
    // Now we can make more vectors by using vInt 
    using vInt = std::vector<int>; 
    
    // vec1 is a vectorof type int 
    vInt v; 
    
    v.push_back(190); 
    v.push_back(180); 
    v.push_back(10); 
    v.push_back(10); 
    v.push_back(27); 
    
    for (auto X : v) { 
        cout << X << " "; 
    } 
    
    return 0; 
}

Output

190 180 10 10 27

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