std::ispunct

Checks if the given character is a punctuation character as classified by the current C locale. The default C locale classifies the characters !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ as punctuation.

The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.

Parameters

Return value

Non-zero value if the character is a punctuation character, zero otherwise.

Notes

Like all other functions from <cctype>, the behavior of std::ispunct is undefined if the argument's value is neither representable as unsigned char nor equal to EOF. To use these functions safely with plain chars (or signed chars), the argument should first be converted to unsigned char:

bool my_ispunct(char ch)
{
    return std::ispunct(static_cast<unsigned char>(ch));
}

Similarly, they should not be directly used with standard algorithms when the iterator's value type is char or signed char. Instead, convert the value to unsigned char first:

int count_puncts(const std::string& s)
{
    return std::count_if(s.begin(), s.end(), 
                      // static_cast<int(*)(int)>(std::ispunct)         // wrong
                      // [](int c){ return std::ispunct(c); }           // wrong
                      // [](char c){ return std::ispunct(c); }          // wrong
                         [](unsigned char c){ return std::ispunct(c); } // correct
                        );
}

Example

#include <iostream>
#include <cctype>
#include <clocale>
 
int main()
{
    unsigned char c = '\xd7'; // the character × (multiplication sign) in ISO-8859-1
 
    std::cout << "ispunct(\'\\xd7\', default C locale) returned "
               << std::boolalpha << (bool)std::ispunct(c) << '\n';
 
    std::setlocale(LC_ALL, "en_GB.iso88591");
    std::cout << "ispunct(\'\\xd7\', ISO-8859-1 locale) returned "
              << std::boolalpha << (bool)std::ispunct(c) << '\n';
}

ispunct('\xd7', default C locale) returned false
ispunct('\xd7', ISO-8859-1 locale) returned true

See also