lib/string/ctype/strisascii.*: Don't special-case ""

It is not intuitive or clear what the right behavior should be for an
empty string.  If we define these APIs as "return true if all characters
in the string belong to the specified character set", then an empty
string should return true.  On the other hand, if you ask me if an empty
string is a numeric string, I might naively say no.

It is irrelevant whether we return true or false for an empty string.
All of the callers already handle correctly the case of an empty string.

This makes the implementation simpler, using the argument only once.
This allows implementing these as macros.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

Author: alejandro-colomar

lib/string/README

@@ -85,8 +85,7 @@ ctype/ - Character classification and conversion functions
 	The functions defined in this file
 	return true
 	if all of the characters of the string
-	belong to the category specified in the function name
-	and the string is not an empty string.
+	belong to the category specified in the function name.
 
     strtoascii.h
 	The functions defined in this file

lib/string/ctype/strisascii.c

@@ -5,9 +5,3 @@
 #include "config.h"
 
 #include "string/ctype/strisascii.h"
-
-#include <stdbool.h>
-
-
-extern inline bool strisdigit_c(const char *s);
-extern inline bool strisprint_c(const char *s);

lib/string/ctype/strisascii.h

@@ -8,27 +8,14 @@
 
 #include "config.h"
 
-#include <stdbool.h>
-
 #include "string/ctype/isascii.h"
 #include "string/strcmp/streq.h"
 #include "string/strspn/stpspn.h"
 
 
-inline bool strisdigit_c(const char *s); // strisdigit - string is [:digit:] C-locale
-inline bool strisprint_c(const char *s); // strisprint - string is [:print:] C-locale
-
-
-inline bool
-strisdigit_c(const char *s)
-{
-	return !streq(s, "") && streq(stpspn(s, CTYPE_DIGIT_C), "");
-}
-inline bool
-strisprint_c(const char *s)
-{
-	return !streq(s, "") && streq(stpspn(s, CTYPE_PRINT_C), "");
-}
+// strisascii_c - string is [:ascii:] C-locale
+#define strisdigit_c(s)  streq(stpspn(s, CTYPE_DIGIT_C), "")
+#define strisprint_c(s)  streq(stpspn(s, CTYPE_PRINT_C), "")
 
 
 #endif  // include guard