[21_7] Use string_view<char> to re-impl ==, !=, <, <= of string

Kernel/Types/string.cpp

@@ -106,22 +106,12 @@ string::operator!= (const char* s) {
 
 bool
 string::operator== (string a) {
-  int i;
-  if (rep->n != a->n) return false;
-  char *S_left= rep->a, *S_right= a->a;
-  for (i= 0; i < rep->n; i++)
-    if (S_left[i] != S_right[i]) return false;
-  return true;
+  return ((string_view<char>) *this) == ((string_view<char>) a);
 }
 
 bool
 string::operator!= (string a) {
-  int i;
-  if (rep->n != a->n) return true;
-  char *S_left= rep->a, *S_right= a->a;
-  for (i= 0; i < rep->n; i++)
-    if (S_left[i] != S_right[i]) return true;
-  return false;
+  return ((string_view<char>) *this) != ((string_view<char>) a);
 }
 
 string
@@ -185,22 +175,12 @@ operator* (string a, const char* b) {
 
 bool
 operator< (string s1, string s2) {
-  int i, n1= N (s1), n2= N (s2), nmin= min (n1, n2);
-  for (i= 0; i < nmin; i++) {
-    if (s1[i] < s2[i]) return true;
-    if (s2[i] < s1[i]) return false;
-  }
-  return n1 < n2;
+  return ((string_view<char>) s1) < ((string_view<char>) s2);
 }
 
 bool
 operator<= (string s1, string s2) {
-  int i, n1= N (s1), n2= N (s2), nmin= min (n1, n2);
-  for (i= 0; i < nmin; i++) {
-    if (s1[i] < s2[i]) return true;
-    if (s2[i] < s1[i]) return false;
-  }
-  return n1 <= n2;
+  return ((string_view<char>) s1) <= ((string_view<char>) s2);
 }
 
 int

Kernel/Types/string.hpp

@@ -14,9 +14,12 @@
 #define STRING_H
 #include "classdef.hpp"
 #include "fast_alloc.hpp"
+#include "lolly/data/string_view.hpp"
 #include "minmax.hpp"
 #include <stdint.h>
 
+using lolly::data::string_view;
+
 class string;
 class string_rep : concrete_struct {
   int   n;
@@ -48,6 +51,10 @@ class string {
   bool         operator== (string s);
   bool         operator!= (string s);
   string       operator() (int start, int end);
+
+  inline operator string_view<char> () {
+    return string_view<char> (rep->a, rep->n);
+  }
 };
 CONCRETE_CODE (string);