Update extralex.cpp

src/crate/extralex.cpp

@@ -1,13 +1,5 @@
 #include "crate.hpp"
 
-bool isUpper(string s) {
-    for (int i = 0; i < s.size(); i++) {
-       if (isupper(s.at(i))) {
-           ;
-       } else {
-           return false; // not uppercase
-       }
-    }
-
-    return true; // no characters caused a false to be returned; thus, it must be uppercase
+bool isUpper(const string& s) {
+    return all_of(s.begin(), s.end(), [](unsigned char c){ return isupper(c); });
 }