+/* Unlike the functions in <ctype.h>, which require an argument in the range
+ of the 'unsigned char' type, the functions here operate on values that are
+ in the 'unsigned char' range or in the 'char' range. In other words,
+ when you have a 'char' value, you need to cast it before using it as
+ argument to a <ctype.h> function:
+
+ const char *s = ...;
+ if (isalpha ((unsigned char) *s)) ...
+
+ but you don't need to cast it for the functions defined in this file:
+
+ const char *s = ...;
+ if (c_isalpha (*s)) ...
+ */
+