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  1. /*
  2. FUNCTION
  3.         <<isalnum>>---alphanumeric character predicate
  4.  
  5. INDEX
  6.         isalnum
  7.  
  8. ANSI_SYNOPSIS
  9.         #include <ctype.h>
  10.         int isalnum(int <[c]>);
  11.  
  12. TRAD_SYNOPSIS
  13.         #include <ctype.h>
  14.         int isalnum(<[c]>);
  15.  
  16.  
  17. DESCRIPTION
  18. <<isalnum>> is a macro which classifies ASCII integer values by table
  19. lookup.  It is a predicate returning non-zero for alphabetic or
  20. numeric ASCII characters, and <<0>> for other arguments.  It is defined
  21. for all integer values.
  22.  
  23. You can use a compiled subroutine instead of the macro definition by
  24. undefining the macro using `<<#undef isalnum>>'.
  25.  
  26. RETURNS
  27. <<isalnum>> returns non-zero if <[c]> is a letter (<<a>>--<<z>> or
  28. <<A>>--<<Z>>) or a digit (<<0>>--<<9>>).
  29.  
  30. PORTABILITY
  31. <<isalnum>> is ANSI C.
  32.  
  33. No OS subroutines are required.
  34. */
  35.  
  36. #include <_ansi.h>
  37. #include <ctype.h>
  38.  
  39. #undef isalnum
  40.  
  41. int
  42. _DEFUN(isalnum,(c),int c)
  43. {
  44.         return(__ctype_ptr__[c+1] & (_U|_L|_N));
  45. }
  46.  
  47.