fixed folder structure + lab4 less hardcode, cleanup

src/Lab6/MainParser.java

@@ -0,0 +1,17 @@
+package Lab6;
+
+import java.util.List;
+
+public class MainParser {
+    public static void main(String[] args) {
+        String input = "(3 + 5) * sqrt(16) + powtwo(5)";
+        List<Token> tokens = Lexer.tokenize(input);
+        System.out.println("Tokens:");
+        tokens.forEach(System.out::println);
+
+        Parser parser = new Parser(tokens);
+        Expr expression = parser.parse();
+        double result = expression.evaluate();
+        System.out.println("Result: " + result);
+    }
+}