Stdnumpunct Byname In C+

In this article, you will learn about the std::numpunct_byname in C++ with its syntax and examples.

What is the std::numpunct_byname?

In C++, you can customize formatting and punctuation for numeric values in locale-sensitive operations using the std::numpunctbyname function. It is contained in the <locale> header of the C++ Standard Library. The thousands separator, grouping sizes, decimal points, and other aspects of numeric formatting can all be defined and controlled via this function. C++ leverages locale settings to decide how to format numeric values when you're performing I/O operations with them, such as integers or floating-point values. You can customize this formatting to fit particular language or regional norms by using the std::numpunctbyname function.

This function is usually used in conjunction with the std::locale class to add locale-specific functionality to streams or other I/O objects. You can ensure that numerical input and output operations follow the anticipated conventions in various locales by configuring numpunct_byname.

Syntax:

It has the following syntax:

template <class charT> class numpunct_byname;

Parameters:

charT: It is of character type.

Member types:

char_type: It a character type function.

wchar_t: It a wide character type.

Example 1:

Let us take an example to illustrate the std::numpunct_byname function in C++.

#include <iostream>
#include <locale>

int main() {
    // Create a locale object using the default system locale
    std::locale loc("");

    // Get a reference to the numpunct facet of the locale
    const std::numpunct<char>& numPunct = std::use_facet<std::numpunct<char>>(loc);

    // Print out the current decimal point and thousands separator
    std::cout << "Decimal point: " << numPunct.decimal_point() << std::endl;
    std::cout << "Thousands separator: " << numPunct.thousands_sep() << std::endl;

    // Create a custom numpunct object with French punctuation
    std::locale frLoc(loc, new std::numpunct_byname<char>("fr_FR.UTF-8"));

    // Set the locale of std::cout to use the custom French locale
    std::cout.imbue(frLoc);

    // Print out a number using the French locale
    double number = 1234567.89;
    std::cout << "Number in French format: " << number << std::endl;

    return 0;
}

Output:

Decimal point: .
Thousands separator: ,
terminate called after throwing an instance of 'std::runtime_error'
  what():  locale::facet::_S_create_c_locale name not valid
Aborted

Explanation:

• ✅ In this example, the <iostream> and <locale> header files are included as needed.
• ✅ The default system locale is used to create a std::locale object.
• ✅ Next, we use the std::use_facet to get a reference to the locale's std::numpunct function.
• ✅ Using the member functions decimalpoint and thousandssep of std::numpunct, we print the current decimal point and thousands separator.
• ✅ Giving the locale name "frFR.UTF-8" causes us to create a custom std::numpunctbyname object with French punctuation.
• ✅ After that, the custom std::numpunct_byname object is combined with the default locale to create a new locale object called frLoc.
• ✅ Using the std::cout.imbue(frLoc) function, we imbue std::cout with the configured French locale.
• ✅ Due to the imbued locale, we can use the std::cout function to print out a number while following the French numeric formatting rules.

Example 2:

Let us take another example to illustrate the std::numpunct_byname function in C++.

#include <iostream>
#include <locale>

int main() {
    // Create a custom numpunct object with a different thousands separator
    std::locale customLoc(std::locale(), new std::numpunct_byname<char>(""));

    // Set the locale of std::cout to use the custom locale
    std::cout.imbue(customLoc);

    // Print out a number using the custom locale
    long long number = 1234567890;
    std::cout << "Number with custom thousands separator: " << number << std::endl;

    return 0;
}

Output:

Number with custom thousands separator: 1,234,567,890

Explanation:

• ✅ In this example, we create a custom std::numpunct_byname object with an empty locale name.
• ✅ It tells us that the thousands separator in the default locale is what we want to use, but we can change it.
• ✅ Using the default locale and the custom std::numpunct_byname object, we can create a std::locale object called customLoc.
• ✅ The custom locale is imbued into the std::cout function through the use of std::cout.imbue(customLoc) .
• ✅ Using the std::cout function, we print a number. The custom thousands separator specified by the custom locale is used.

Conclusion:

In conclusion, a reliable method for adjusting numeric formatting in locale-sensitive operations is offered by the C++ std::numpunctbyname function. Applications that follow particular linguistic or regional conventions can be created by giving developers the ability to define and control elements like decimal points, thousands separators, and grouping sizes. In this article, we have learned how to use std::numpunctbyname to customize numerical output to various locales and make sure that numbers are shown in a way that is recognizable to users through examples. This feature allows for fine-grained control over numerical formatting, which improves the usability and accessibility of C++ programs in a variety of cultural contexts. It can be used to apply new punctuation rules or adjust thousands of separators.