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      std::islower

      From cppreference.com
      <cpp‎ |string‎ |byte
       
       
       
       
      Defined in header<cctype>
      int islower(int ch);

      Checks if the given character is classified as a lowercase character according to the current C locale. In the default"C" locale,std::islower returns a nonzero value only for the lowercase letters (abcdefghijklmnopqrstuvwxyz).

      Ifislower returns a nonzero value, it is guaranteed thatstd::iscntrl,std::isdigit,std::ispunct, andstd::isspace return zero for the same character in the same C locale.

      The behavior is undefined if the value ofch is not representable asunsignedchar and is not equal toEOF.

      Contents

      [edit]Parameters

      ch - character to classify

      [edit]Return value

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

      [edit]Notes

      Like all other functions from<cctype>, the behavior ofstd::islower is undefined if the argument's value is neither representable asunsignedchar nor equal toEOF. To use these functions safely with plainchars (orsignedchars), the argument should first be converted tounsignedchar:

      bool my_islower(char ch){return std::islower(static_cast<unsignedchar>(ch));}

      Similarly, they should not be directly used with standard algorithms when the iterator's value type ischar orsignedchar. Instead, convert the value tounsignedchar first:

      int count_lowers(conststd::string& s){returnstd::count_if(s.begin(), s.end(),// static_cast<int(*)(int)>(std::islower)         // wrong// [](int c){ return std::islower(c); }           // wrong// [](char c){ return std::islower(c); }          // wrong[](unsignedchar c){return std::islower(c);}// correct);}

      [edit]Example

      Run this code
      #include <cctype>#include <clocale>#include <iostream> int main(){unsignedchar c='\xe5';// letter å in ISO-8859-1 std::cout<<"islower(\'\\xe5\', default C locale) returned "<<std::boolalpha<<(bool)std::islower(c)<<'\n'; std::setlocale(LC_ALL,"en_GB.iso88591");std::cout<<"islower(\'\\xe5\', ISO-8859-1 locale) returned "<<std::boolalpha<<(bool)std::islower(c)<<'\n'; }

      Possible output:

      islower('\xe5', default C locale) returned falseislower('\xe5', ISO-8859-1 locale) returned true

      [edit]See also

      checks if a character is classified as lowercase by a locale
      (function template)[edit]
      checks if a wide character is lowercase
      (function)[edit]
      C documentation forislower
      ASCII valuescharacters

      iscntrl
      iswcntrl

      isprint
      iswprint

      isspace
      iswspace

      isblank
      iswblank

      isgraph
      iswgraph

      ispunct
      iswpunct

      isalnum
      iswalnum

      isalpha
      iswalpha

      isupper
      iswupper

      islower
      iswlower

      isdigit
      iswdigit

      isxdigit
      iswxdigit

      decimalhexadecimaloctal
      0–8\x0–\x8\0–\10control codes (NUL, etc.)≠000000000000
      9\x9\11tab (\t)≠00≠0≠000000000
      10–13\xA–\xD\12–\15whitespaces (\n,\v,\f,\r)≠00≠0000000000
      14–31\xE–\x1F\16–\37control codes≠000000000000
      32\x20\40space0≠0≠0≠000000000
      33–47\x21–\x2F\41–\57!"#$%&'()*+,-./0≠000≠0≠0000000
      48–57\x30–\x39\60–\7101234567890≠000≠00≠0000≠0≠0
      58–64\x3A–\x40\72–\100:;<=>?@0≠000≠0≠0000000
      65–70\x41–\x46\101–\106ABCDEF0≠000≠00≠0≠0≠000≠0
      71–90\x47–\x5A\107–\132GHIJKLMNOP
      QRSTUVWXYZ      		0≠000≠00≠0≠0≠0000
      91–96\x5B–\x60\133–\140[\]^_`0≠000≠0≠0000000
      97–102\x61–\x66\141–\146abcdef0≠000≠00≠0≠00≠00≠0
      103–122\x67–\x7A\147–\172ghijklmnop
      qrstuvwxyz      		0≠000≠00≠0≠00≠000
      123–126\x7B–\x7E\172–\176{|}~0≠000≠0≠0000000
      127\x7F\177backspace character (DEL)≠000000000000
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