std::isblank - cppreference.com (original) (raw)

| | | | | ---------------------- | | ------------- | | int isblank( int ch ); | | (since C++11) |

Checks if the given character is a blank character as classified by the currently installed C locale. Blank characters are whitespace characters used to separate words within a sentence. In the default C locale, only space (0x20) and horizontal tab (0x09) are classified as blank characters.

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

[edit] Parameters

[edit] Return value

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

[edit] Notes

Like all other functions from , the behavior of std::isblank 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_isblank(char ch) { return std::isblank(static_cast(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_blanks(const std::string& s) { return std::count_if(s.begin(), s.end(), // static_cast<int(*)(int)>(std::isblank) // wrong // [](int c){ return std::isblank(c); } // wrong // [](char c){ return std::isblank(c); } // wrong [](unsigned char c){ return std::isblank(c); } // correct ); }

[edit] See also