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std::isspace

Defined in header <cctype>
int isspace( int ch );

Checks if the given character is whitespace character as classified by the currently installed C locale. In the default locale, the whitespace characters are the following:

  • space (0x20, ' ')
  • form feed (0x0c, '\f')
  • line feed (0x0a, '\n')
  • carriage return (0x0d, '\r')
  • horizontal tab (0x09, '\t')
  • vertical tab (0x0b, '\v')

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

Parameters

ch - character to classify

Return value

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

Notes

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

See also

checks if a character is classified as whitespace by a locale
(function template)
checks if a wide character is a space character
(function)
ASCII values characters

iscntrl
iswcntrl.

isprint
iswprint.

isspace
iswspace.

isblank
iswblank.

isgraph
iswgraph.

ispunct
iswpunct.

isalnum
iswalnum.

isalpha
iswalpha.

isupper
iswupper.

islower
iswlower.

isdigit
iswdigit.

isxdigit
iswxdigit.

decimal hexadecimal octal
0–8 \x0\x8 \0\10 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0
9 \x9 \11 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
10–13 \xA\xD \12\15 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
14–31 \xE\x1F \16\37 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0
32 \x20 \40 space 0 ≠0 ≠0 ≠0 0 0 0 0 0 0 0 0
33–47 \x21\x2F \41\57 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
48–57 \x30\x39 \60\71 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0
58–64 \x3A\x40 \72\100 :;<=>[email protected] 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
65–70 \x41\x46 \101\106 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0
71–90 \x47\x5A \107\132 GHIJKLMNOP
QRSTUVWXYZ
0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
91–96 \x5B\x60 \133\140 [\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
97–102 \x61\x66 \141\146 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0
103–122 \x67\x7A \147\172 ghijklmnop
qrstuvwxyz
0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
123–126 \x7B\x7E \172\176 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
127 \x7F \177 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0

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