Essentially, the C++ standard library provides the most common fundamental data structures together with the fundamental algorithms used on them.

The facilities provided by the standard library can be classified like:

• Run-time language support (e.g., for allocation and run-time type information).
• The C standard library (with very minor modifications to minimize violations of the type system).
• Strings (with support for international character sets and localization).
• Support for regular expression matching.
• I/O streams is an extensible framework for input and output to which users can add their own types, streams, buffering strategies, locales, and character sets.
• A framework of containers (such as vector and map) and algorithms (such as find(), sort(), and merge())
• Support for numerical computation, such as standard mathematical functions, complex numbers, vectors with arithmetic operations, and random number generators.
• Support for concurrent programming, including threads and locks.
• Utilities to support template metaprogramming (e.g., type traits), STL-style generic programming.
• “Smart pointer” for resource management and an interface to garbage collectors.
• Special-purpose containers, such as array, bitset and tuple.

Every standard-library facility is provided through some standard header. For example:

#include<string> // make the standard string facilities accessible
#include<list>

using namespace std; // make std names available without std:: prefix

string s {"C++ is a general−purpose programming language"}; // OK: string is std::string

This makes the standard string and list available.

Headers from the C standard library, such as <stdlib.h> are provided. For each such header there is also a version with its name prefixed by c and the .h removed. This version, such as <cstdlib> places its declarations in the std namespace.

String

String concatenation:

string compose(const string& name, const string& domain) 
{
    return name + '@' + domain; 
}

auto addr = compose("dmr","bell−labs.com");

• A string is mutable.
  • s1 += '\n'
  • string s = name.substr(6,10);
  • name.replace(0,5,"nicholas");
  • name[0] = toupper(name[0]);
• strings can be compared against each other and against string literals.
  • str1 == str2
  • str1 == 'yes'
• string implementation
  • Short string values are kept in the string object itself and only longer strings are placed on free store.
    • Short: string s1 {"Annemarie"};
    • Long: string s2 {"Annemarie Stroustrup"};
    • Good if the memory allocation is costly (multi-threaded) and memory fragmentation caused by many different lengths of strings.
• To handle multipe character sets, string is really an alias for a general template basic_string with the character type char.
  • We can handle different char type, like Jchar and unicode.

template<typename Char> 
class basic_string {
// ... string of Char ... 
};
using string = basic_string<char>

// for Jchar type
using Jstring = basic_string<Jchar>;

Regex

regex pat (R"(\w{2}\s∗\d{5}(−\d{4})?)"); // US postal code pattern: XXddddd-dddd and variants