newlib/libc/ctype/isalpha.c

   1 /*
   2 FUNCTION
   3         <<isalpha>>, <<isalpha_l>>---alphabetic character predicate
   4
   5 INDEX
   6         isalpha
   7
   8 INDEX
   9         isalpha_l
  10
  11 SYNOPSIS
  12         #include <ctype.h>
  13         int isalpha(int <[c]>);
  14
  15         #include <ctype.h>
  16         int isalpha_l(int <[c]>, locale_t <[locale]>);
  17
  18 DESCRIPTION
  19 <<isalpha>> is a macro which classifies singlebyte charset values by table
  20 lookup.  It is a predicate returning non-zero when <[c]> represents an
  21 alphabetic ASCII character, and 0 otherwise.  It is defined only if
  22 <[c]> is representable as an unsigned char or if <[c]> is EOF.
  23
  24 <<isalpha_l>> is like <<isalpha>> but performs the check based on the
  25 locale specified by the locale object locale.  If <[locale]> is
  26 LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
  27
  28 You can use a compiled subroutine instead of the macro definition by
  29 undefining the macro using `<<#undef isalpha>>' or `<<#undef isalpha_l>>'.
  30
  31 RETURNS
  32 <<isalpha>>, <<isalpha_l>> return non-zero if <[c]> is a letter.
  33
  34 PORTABILITY
  35 <<isalpha>> is ANSI C.
  36 <<isalpha_l>> is POSIX-1.2008.
  37
  38 No supporting OS subroutines are required.
  39 */
  40
  41 #include <_ansi.h>
  42 #include <ctype.h>
  43
  44 #undef isalpha
  45 int
  46 isalpha (int c)
  47 {
  48         return(__CTYPE_PTR[c+1] & (_U|_L));
  49 }