Is pair a struct?

All members of the type pair are public, because the type is declared as a struct rather than as a class .

What is std :: pair?

std::pair is a class template that provides a way to store two heterogeneous objects as a single unit. A pair is a specific case of a std::tuple with two elements.

What is struct pair in C++?

Pair is used to combine together two values that may be different in type. Pair provides a way to store two heterogeneous objects as a single unit. It is basically used if we want to store tuples. The pair container is a simple container defined in header consisting of two data elements or objects.

Is std :: pair contiguous?

std::pair is a struct, the standard says the compiler determines the layout though the order must be maintained, so in the instance of std::pair your compiler may decide to place 3-byte padding after each char for optimal alignment, so no you can’t assume contiguous memory layout – end of story.

What containers always use std pair?

The standard library uses std::pair in the interface of associative containers where the pair groups together the key and the value. So, when you use such containers, you need to use pairs as well.

Is pair mutable in C++?

The answer in something like std::pair is a flat “no”. There is no case for controlling access to members in a class whose sole purpose is to contain those members.

What is the difference between MAP and pair in C++?

std:pair holds exactly two objects. std:map hold a collection of paired objects.

How are pairs compare in C++?

With C++ pair, use the comparison (==) operator: The comparison operator measures the first and second values of two sets, say pair1 and pair2, to see whether pair1. first is equal to pair2. first or not, and whether pair1. second is equal to pair2.

How do I choose a STL container?

There are some general rules of thumb that will guide you through most situations:

  1. Use sequential containers when you need to access elements by position. Use std:vector as your default sequential container, especially as an alternative to built-in arrays.
  2. Use associative containers when you need to access elements by key.

Is C++ tuple mutable?

The tuple itself isn’t mutable (i.e. it doesn’t have any methods that for changing its contents). Likewise, the string is immutable because strings don’t have any mutating methods. The list object does have mutating methods, so it can be changed.