What Is The Integer Sequence (std::integer

In modern programming sometimes we want to use a sequence of integers that are created at compile-time. In C++14, the std::integer_sequence is a class template for the sequence of integers that is generated at compile-time. In this post, we explain what integer sequence (std::integer_sequence) is in modern programming.

What is the integer sequence (std::integer_sequence) in C++ 14?

In C++14, the std::integer_sequence is a class template defined in a header that can be used for the sequence of integers generated at compile-time. In some cases, looping through a range of numbers whose span is unknown is used and, in these cases, we can use the std::integer_sequence integer sequence. Thus, we can create a sequence of integers at compile time. Our application knows the sequence of integers before it runs, and we use them on runtime as a package. In other words, the std::integer_sequence is used to hold a sequence of integers which can be turned into a parameter pack. We can use integer_sequence in template programming or meta-programming algorithms, and this will make our code faster and less complex.

In C++14, a simple syntax for the std::integer_sequence can be written as shown below.

template< class T, T... Ints > class integer_sequence;

Here, T is the type of integers and val is a parameter pack of integers.

Is there a simple integer sequence (std::integer_sequence) example in C++ 14?

Here is a simple example how we can use std::integer_sequence.

template <typename T, T... val> void print_sequence2(std::integer_sequence<T, val...>)

{

( (std::cout << val << ','), ...);

}

Here is another example with std::initializer_list.

template <typename T, T... val> void print_sequence(std::integer_sequence<T, val...>)

{

std::initializer_list<bool>{ bool(std::cout << val << ',')... };

std::cout << std::endl;

}

Is there a full integer sequence (std::integer_sequence) example in C++ 14?

Here is a full integer sequence (std::integer_sequence) example in C++14 and C++17.

#include <iostream>

#include <utility>

template <typename T, T... val> void print_sequence(std::integer_sequence<T, val...>)

{

std::initializer_list<bool>{ bool(std::cout << val << ',')... };

std::cout << std::endl;

}

template <typename T, T... val> void print_sequence2(std::integer_sequence<T, val...>)

{

( (std::cout << val << ','), ...);

}

int main()

{

using mysequence = std::integer_sequence<int, 9, 8, 7, 6, 5>;

print_sequence( mysequence() );

print_sequence(std::integer_sequence<int, 1, 2, 3>());

print_sequence2( mysequence() );

print_sequence2(std::integer_sequence<int, 1, 2, 3>());

system("pause");

return 0;

}

For more information, please see https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html

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What Is The Integer Sequence (std::integer_sequence) In C++ 14