Extract public compiler API into its own header file

src/compiler/rules/character_range.cpp

@@ -0,0 +1,44 @@
+#include "compiler.h"
+
+namespace tree_sitter {
+    using std::string;
+    
+    namespace rules {
+        static const char MAX_CHAR = '\xff';
+        
+        CharacterRange::CharacterRange(char value) : min(value), max(value) {}
+        CharacterRange::CharacterRange(char min, char max) : min(min),  max(max) {}
+        
+        bool CharacterRange::operator==(const CharacterRange &other) const {
+            return min == other.min && max == other.max;
+        }
+        
+        bool CharacterRange::operator<(const CharacterRange &other) const {
+            if (min < other.min) return true;
+            if (min > other.min) return false;
+            if (max < other.max) return true;
+            return false;
+        }
+        
+        string escape_character(char input) {
+            switch (input) {
+                case '\0':
+                    return "<EOF>";
+                case MAX_CHAR:
+                    return "<MAX>";
+                default:
+                    return string() + input;
+            }
+        }
+        
+        string CharacterRange::to_string() const {
+            if (min == 0 && max == MAX_CHAR)
+                return "<ANY>";
+            if (min == max)
+                return escape_character(min);
+            else
+                return string() + escape_character(min) + "-" + escape_character(max);
+        }
+    }
+}
+