CodeCogs

Container for storing elements of type char

Definition

The std::string class template is defined in the standard header <string>, and in the nonstandard backward-compatibility header <string.h>.

namespace std {
            typedef basic_string<char> string;
}

Description

The class template basic_string stores and manipulates sequences of type char. std::string is an STL container which is part of basic_string for storing elements of type char.

Member Functions

Operation	Description
`constructor`	Create or copy a string
`destructor`	Destroys a string
=, assign()	Assign a new value
swap()	Swaps values between two strings
+=, append(), push_back()	Append characters
insert()	Inserts characters
erase()	Deletes characters
resize()	Changes the number of characters (deletes or appends characters at the end)
replace()	Replaces characters
+	Concatenates strings
==, !=, <, <=, >, >=, compare()	Compare strings
size(), length()	Return the number of characters
max_size()	Returns the maximum possible number of characters
empty()	Returns if the string is empty
capacity()	Returns the number of characters that can held without be reallocation
[], at()	Access a character
>>, getline()	Read the value from a stream
<<	Writes the value to a stream
copy()	Copies or writes the contents to a C-string
c_str()	Returns the value as C-string
data()	Returns the value as character array
substr()	Returns a certain substring
get_allocator()	Returns the allocator

Iterators

Operation	Description
begin(), cbegin()	Returns an iterator to the beginning
end(), cend()	Returns an iterator to the end
rbegin(), crbegin()	Returns a reverse iterator to the beginning
rend(), crend()	Returns a reverse iterator to the end

Search

Operation	Description
find()	Find characters in the string
rfind()	Find the last occurrence of a substring
find_first_of()	Find first occurrence of characters
find_first_not_of	Find first absence of characters
find_last_of	Find last occurrence of characters
find_last_not_of	Find last absence of characters

Numeric conversions

Operation	Description
stoi(), stol(), stoll()	Converts a string to an signed integer
stoul(), stoull()	Converts a string to an unsigned integer
stof(), stod(), stold()	Converts a string to an floating point value
to_string()	Converts an integral or floating point value to string
to_wstring()	Converts an integral or floating point value to wstring

References

http://msdn.microsoft.com/en-us/
Nicolai M. Josuttis: "The C++ Standard Library"

Example 1

Problem

This simple program shows how to read and how to print out a string.

Workings

#include <iostream>
#include <string>

using namespace std;

int main()
{
    // Enter text into a string
    string qWord;
    cout << "Enter a word: ";
    cin >> qWord;
    cout << "The word is: " << qWord << endl;

    return 0;
}

Solution

Output:

Enter a word: Hello!
The word is: Hello!

Example 2

Problem

The following program is converting from string to double and from double to string.

Workings

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main() 
{
    // Conversion from string to double
    stringstream qStringToDouble;
    string qString("3.14159");
    qStringToDouble << qString;
    double dConvertedDouble;
    qStringToDouble >> dConvertedDouble;
    // Output the double result
    cout << dConvertedDouble << endl;

    // Conversion from double to string
    stringstream qDoubleToString;
    double dDouble = 2.71828;
    qDoubleToString << dDouble;
    string qConvertedString(qDoubleToString.str());
    // Output the string
    cout << qConvertedString << endl;

    return 0;
}

Solution

Output:

3.14159
2.71828

Example 3

Problem

This example of program is sorting several strings in alphabetical order.

Workings

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    string qName1("Hello!");
    string qName3("C++");
    string qName2("Algorithms");
    string qName4("Graphics");

    vector<string> qNames;
    qNames.push_back(qName1);
    qNames.push_back(qName2);
    qNames.push_back(qName3);
    qNames.push_back(qName4);

    cout << "Unsorted list:" << endl;
    for (unsigned int uiIndex = 0; uiIndex < 4; ++uiIndex) {
        cout << qNames[uiIndex] << endl;
    }

    sort(qNames.begin(), qNames.end());

    cout << endl << "Sorted list:" << endl;
    for (unsigned int uiIndex = 0; uiIndex < 4; ++uiIndex) {
        cout << qNames[uiIndex] << endl;
    }

    return 0;
}

Solution

Output:

Unsorted list:
Hello!
C++
Algorithms
Graphics

Sorted list:
Algorithms
C++
Graphics
Hello!

References

http://xoax.net/