Tuple in C++

Hello Folks!!!

Welcome to this C++ tutorial where you are going to learn about an interesting topic of C++ which is Tuple. So let’s dove into the tutorial…

• If you are familiar with the Python language then you must have gone through “tuples”. But if you haven’t heard about this term then let’s first discuss that.
• A “tuple” is used to store heterogeneous data together. It might be homogeneous data but it allows heterogeneous data also to be stored together.
• You can consider “tuple” as a substitute for a struct(which is mainly a ‘C’ language feature). In “struct,” we could create a structure that can have multiple types of data.
• Similarly, we can create “tuples” to store multiple type elements. In C++, the number of elements in a tuple must be fixed. For instance,

tuple < string , float , int > tuple_object ;

• Here you cannot insert one more element at runtime. So you need to specify all the elements the tuple can store at the time of defining it.
• The above example is also the syntax for a tuple in C++ where you need to specify the data types inside the angular brackets “< >” that the tuple can store.
• Now you must have understood a little about “tuples”. So now let’s understand how to initialize a tuple in C++.

Initializing tuple

• For initializing a tuple we make use of the built-in function make_tuple(). This function takes the literals as the arguments in the same order as they are specified inside the angular brackets.

For instance,

tuple< string , int , string > Tup = make_tuple( "String1" , 2020 , "String2" );

Accessing values of the tuple

• At times we often need one of the elements from the tuple. So to access each element of the tuple we use the following syntax,

get<index> (tuple_object) ;

• Here the angular brackets are used for templates for specifying the template parameters. Here we use templates to use indexing within the tuple.
• As templates are processed at compile-time, the parameters are also processed at compile-time. That is why these parameters need to be a constant value.
• For instance, you cannot write like this,

int i = 0;

get< i > (tuple_object) ; //This will cause compile-time error

• But if you specify const at the time of defining ‘i’ then you can it as an index.

Now let’s understand whatever we have discussed with the help of a program,

Program for illustrating tuple

// C++ program illustrating
// implementation of tuple

#include <iostream>
#include <tuple>	//Header file to use tuple
using namespace std;

int main(void)
{
  // Defining a tuple "Tup"
  tuple<string , int , char > Tup = make_tuple("String" , 1 , 'a');

  // Printing values inside the tuple
  cout << get<0>(Tup) << " "<< get<1>(Tup) << " "<< get<2>(Tup);

  // Change value at index '1'
  get<1>(Tup) = 2;

  // Display the updated value
  cout<<"\n"<<get<1>(Tup);

  return 0;
}

Run this code online
If you run the above program you will get the following output,

String 1 a
2

Using tie() with tuple

• tie function is used to unpack a tuple. So let’s say you have a tuple with data types as <char, int, int >. Using tie function you can get these values of a tuple as an individual. Let’s understand this with an example,

tuple < char , int , int > Tup ('a' , 1 , 10)

char p;
int q, r;

tie( p , q , r) = Tup;   // This will give you
                       // p = 'a'  ,  q = 1  &  r = 10

• There’s one more thing about tie function. Say if you don’t want some members to be stored or unpacked, you can use ignore in place of that. For instance,

tuple < char , int , int > Tup ('a' , 1 , 10)

char p;
int  r;

tie( p , ignore , r) = Tup;   // This will give you
                            // p = 'a'  &  r = 10

• I think that’s much for this tutorial. So I hope you understood the concept of the tuple in C++. Keep practicing to understand it more clearly.

Thanks for going through this tutorial.

Comment down your queries.