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      std::isalpha

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

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

      • uppercase lettersABCDEFGHIJKLMNOPQRSTUVWXYZ
      • lowercase lettersabcdefghijklmnopqrstuvwxyz

      In locales other than"C", an alphabetic character is a character for whichstd::isupper() orstd::islower() returns non-zero or any other character considered alphabetic by the locale. In any case,std::iscntrl(),std::isdigit(),std::ispunct() andstd::isspace() will return zero for this character.

      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 an alphabetic character, zero otherwise.

      [edit]Notes

      Like all other functions from<cctype>, the behavior ofstd::isalpha 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_isalpha(char ch){return std::isalpha(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_alphas(conststd::string& s){returnstd::count_if(s.begin(), s.end(),// static_cast<int(*)(int)>(std::isalpha)         // wrong// [](int c){ return std::isalpha(c); }           // wrong// [](char c){ return std::isalpha(c); }          // wrong[](unsignedchar c){return std::isalpha(c);}// correct);}

      [edit]Example

      Demonstrates the use ofstd::isalpha with different locales (OS-specific).

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

      Possible output:

      isalpha('\xdf', default C locale) returned falseisalpha('\xdf', ISO-8859-1 locale) returned true

      [edit]See also

      checks if a character is classified as alphabetic by a locale
      (function template)[edit]
      checks if a wide character is alphabetic
      (function)[edit]
      C documentation forisalpha
      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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