C++ Boost String Algorithms Library

The Boost String Algorithms Library provides a generic implementation of string-related algorithms which are missing in STL. It is an extension to the algorithms library of STL and it includes trimming, case conversion, predicates and find/replace functions. All of them come in different variants so it is easier to choose the best fit for a particular need. The implementation is not restricted to work with a particular container (like basic_string), rather it is as generic as possible. This generalization is not compromising the performance since algorithms are using container specific features when it means a performance gain.

Converting a string to uppercase and lowercase. STL has a nice way of converting the character case. Unfortunately, it works only for a single character and we want to convert a string,

to_upper() and to_lower() convert the case of characters in a string using a specified locale.
to_upper_copy() and to_lower_copy() returns the copy of the converted string.

Examples:

CPP

#include <boost/algorithm/string.hpp>
#include <iostream>

using namespace std;
using namespace boost::algorithm;

int main()
{
    string str("Hello");
    string upper_s;
    string lower_s;

    cout << "Actual string: "
         << str << endl;

    to_upper(str);
    cout << "Actual string converted to uppercase: "
         << str << endl;

    to_lower(str);
    cout << "Actual string converted to lowercase: "
         << str << endl;

    str = "Hello";
    upper_s = to_upper_copy(str);
    lower_s = to_lower_copy(str);

    cout << "Converted Uppercase string: "
         << upper_s << endl;
    cout << "Converted Lowercase string: "
         << lower_s << endl;

    return 0;
}

Output:

Actual string: Hello
Actual string converted to uppercase: HELLO
Actual string converted to lowercase: hello
Converted Uppercase string: HELLO
Converted Lowercase string: hello

To remove characters from a string Boost.StringAlgorithms provides several functions you can use to delete individual characters from a string.

erase_first_copy() will remove the first occurrence in the source string.
erase_nth_copy() will remove the nth occurrence in the source string.
erase_all_copy() will remove all occurrences of a particular character from a string.
To shorten a string by a specific number of characters on either end, use the functions erase_head_copy() and erase_tail_copy().

Example

CPP

#include <boost/algorithm/string.hpp>
#include <cstdlib>
#include <iostream>
#include <string>

using namespace std;
using namespace boost::algorithm;

int main()
{

    string s = "geeksforgeeks";
    cout << erase_first_copy(s, "g") << '\n';
    cout << erase_nth_copy(s, "g", 0) << '\n';
    cout << erase_last_copy(s, "g") << '\n';
    cout << erase_all_copy(s, "g") << '\n';
    cout << erase_head_copy(s, 5) << '\n';
    cout << erase_tail_copy(s, 1) << '\n';
    return 0;
}

Output:

eeksforgeeks
eeksforgeeks
geeksforeeks
eeksforeeks
forgeeks
geeksforgeek

To replace characters from a string Boost.StringAlgorithms provides several functions you can use to replace individual characters from a string.

replace_first_copy() will replace the first occurrence in the source string.
replace_nth_copy() will replace the nth occurrence in the source string.
replace_all_copy() will replace all occurrences of a particular character from a string.

Example

CPP

#include <boost/algorithm/string.hpp>
#include <cstdlib>
#include <iostream>
#include <string>

using namespace std;
using namespace boost::algorithm;

int main()
{

    string s = "geeks_for_geeks";
    cout
        << replace_first_copy(s, "_", "-")
        << '\n';
    cout
        << replace_last_copy(s, "_", "-")
        << '\n';
    cout
        << replace_all_copy(s, "_", "-")
        << '\n';
    return 0;
}

Output:

geeks-for_geeks
geeks_for-geeks
geeks-for-geeks

Reference: https://www.boost.org/doc/libs/1_70_0/doc/html/string_algo/reference.html

C++ Boost String Algorithms Library

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