fixed folder structure + lab4 less hardcode, cleanup

src/Lab6/Lexer.java

@@ -0,0 +1,51 @@
+package Lab6;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Lexer {
+    public static List<Token> tokenize(String input) {
+        List<Token> tokens = new ArrayList<>();
+        input = input.replaceAll("\\s", "");
+        int i = 0;
+        while (i < input.length()) {
+            char ch = input.charAt(i);
+            if (Character.isDigit(ch)) {
+                StringBuilder sb = new StringBuilder();
+                while (i < input.length() && (Character.isDigit(input.charAt(i)) || input.charAt(i) == '.')) {
+                    sb.append(input.charAt(i));
+                    i++;
+                }
+                tokens.add(new Token(TokenType.NUMBER, sb.toString()));
+            } else if (Character.isLetter(ch)) {
+                StringBuilder sb = new StringBuilder();
+                while (i < input.length() && Character.isLetter(input.charAt(i))) {
+                    sb.append(input.charAt(i));
+                    i++;
+                }
+                tokens.add(new Token(TokenType.FUNCTION, sb.toString()));
+            } else {
+                switch (ch) {
+                    case '(':
+                        tokens.add(new Token(TokenType.LPAREN, "("));
+                        i++;
+                        break;
+                    case ')':
+                        tokens.add(new Token(TokenType.RPAREN, ")"));
+                        i++;
+                        break;
+                    case ',':
+                        tokens.add(new Token(TokenType.COMMA, ","));
+                        i++;
+                        break;
+                    default:
+                        tokens.add(new Token(TokenType.OPERATOR, String.valueOf(ch)));
+                        i++;
+                        break;
+                }
+            }
+        }
+        tokens.add(new Token(TokenType.EOF, ""));
+        return tokens;
+    }
+}