Using Standard Libraries in C++

Using Standard Libraries in C++

📘 Overview The C++ Standard Library provides reusable facilities for input and output, strings, containers, and algorithms. Programs access these facilities through standard headers and names usually qualified with std::.

🧠 Key Idea Include the appropriate header, select a library facility that matches the task, and follow its interface requirements. Containers manage data, while algorithms operate on data through iterator ranges.

⚔️ Core Details: - Headers declare library facilities: <iostream> provides standard streams, <string> provides std::string, and <vector> provides std::vector. - The scope-resolution operator qualifies library names: std::cout identifies cout in namespace std. - std::vector<int> values{3, 1, 2}; creates a resizable sequence of integers. - Most range-based algorithms use a half-open iterator range: the first iterator is included and the last iterator is excluded. - With <algorithm> included, std::sort(values.begin(), values.end()); sorts a vector in ascending order by default. - For std::vector, at() checks bounds and throws std::out_of_range for an invalid index.

🎯 Why It Matters: - Standard facilities reduce custom implementation work and make program intent easier to recognize. - Standardized interfaces support source portability across conforming C++ implementations. - Understanding iterator validity and function preconditions prevents incorrect library use, including undefined behavior. - Container and algorithm choices affect performance as programs process larger collections.

🧠 Quick Recall: - std:: - Qualifies a name within the standard-library namespace. - std::cin and std::cout - Standard input and output stream objects declared in <iostream>. - std::string - A character-sequence class declared in <string>. - Half-open range - Includes the starting iterator and excludes the ending iterator; end() is not dereferenceable. - std::sort - An algorithm declared in <algorithm> that requires random-access iterators.