Update 10.0

Changes in this update:
- Added multiple features:
    - Added the keyword "import"
    - Added the modulo operator for arithmetic operations
    - Added the ability to comment in the source code
- Fixes:
   - Fixed nearly all the links in the documentation of this project
   - Functions cannot have the same name anymore (Function overloading does not work - It was not even implemented before)
    - Fixed comments in the source code

Documentation/Atithmetic operations.md

@@ -32,7 +32,7 @@ The result of such arithmetic operations can be used in the source code for diff
 <br/>
 
 # Available arithmetic operators:
-Currently, there are a total of four operators, which can be used in arithmetic operations:
+Currently, there are a total of five operators, which can be used in arithmetic operations:
 
 <br/>
 
@@ -83,3 +83,15 @@ The operator `/` is used to divide multiple values. Remember that there is no kn
 ```
 
 <br/>
+
+## The operator `%`:
+The operator `%` is used to get the rest of a division.
+
+### Example:
+```Lisp
+(defun main () (
+    (princ (% 5 2)) ;Translates to 5 % 2
+))
+```
+
+<br/>

Documentation/Control characters.md

@@ -99,7 +99,7 @@ This character represents a form feed.
 
 <br/>
 
-## `r`:
+## `\r`:
 This character represents a carriage return.
 
 <br/>

Documentation/Keywords.md

@@ -19,51 +19,58 @@ Currently, there are multiple keywords available with this Lisp dialect.
 <br/>
 
 ### Keywords regarding variables:
-[`var`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#var)
+[`var`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#var)
 <br/>
 This keyword is used to declare a new variable.
 
-[`setf`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#setf)
+[`setf`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#setf)
 <br/>
 This keyword is used to change the value of any variable.
 
 <br/>
 
 ### Keywords for in- and output:
-[`princ`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#princ-princln)
+[`princ`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#princ-princln)
 <br/>
 This keyword is used to output anything in the terminal.
 
-[`princln`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#princ-princln)
+[`princln`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#princ-princln)
 <br/>
 This keyword is used to output anything in the terminal and adds a line break afterwards.
 
-[`scan`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#scan)
+[`scan`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#scan)
 <br/>
 This keyword is used to scan an input from the user.
 
 <br/>
 
 ### Keywords for control structures:
-[`if`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#if)
+[`if`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#if)
 <br/>
 This keyword indicates an if-statement.
 
-[`while`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#while)
+[`while`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#while)
 <br/>
 This keyword indicates a while-loop.
 
 <br/>
 
 ### Keywords for functions:
-[`defun`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#defun)
+[`defun`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#defun)
 <br/>
 This keyword is used to define a new function.
 
-[`return`](https://github.com/ChosenChris/LispInterpreter/tree/main/Keywords.md#return)
+[`return`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#return)
 <br/>
 This keyword is used to exit a function and return a value.
 
+<br/>
+
+### Other keywords:
+[`import`](https://github.com/ChosenChris/LispInterpreter/blob/main/Documentation/Keywords.md#import)
+<br/>
+This keyword is used to import source code from another file.
+
 <br/>
 <br/>
 <br/>
@@ -344,3 +351,37 @@ This element is returned by the function.
 ```
 
 <br/>
+<br/>
+<br/>
+
+## `import`:
+The keyword `import` is used to import source code from another file. The functions etc. of the other file can be used in the current file as well.
+<br/>
+**IMPORTANT:** Please make sure that you do not create a StackOverflow when using the import statement.
+
+<br/>
+
+### Further elements in this list:
+_file name_
+<br/>
+This element represents the file name, which should be imported.
+
+<br/>
+
+### Example:
+```Lisp
+;File: code.lsp
+(defun mul (a b) (
+    (return (* a b))
+))
+```
+```Lisp
+;File: main.lsp
+(import "code.lsp")
+
+(defun main () (
+    (princ mul(2 5)) ;Calls the "mul()"-function from the other file.
+))
+```
+
+<br/>

src/Program.java

@@ -1,5 +1,6 @@
 import java.util.Scanner;
 
+import errorHandling.ReturnValueTypes;
 import interpreter.*;
 
 
@@ -57,8 +58,11 @@ else if (sLowerCaseInput.length() >= 4 && sLowerCaseInput.substring(0, 4).equals
 				String sFilename = sInput.substring(sInput.indexOf(' ') + 1, sInput.length());
 				//Quellcode ueber den Controller ausfueheren:
 				Controller controllerObj = new Controller(sFilename);
-				controllerObj.startController();
+				int nReturnValue = controllerObj.startController();
 				System.out.println("\n");
+				if (nReturnValue != ReturnValueTypes.SUCCESS) {
+					printErrorMessage("Error: ", nReturnValue, "\n");
+				}
 			}
 
 			else {
@@ -67,4 +71,93 @@ else if (sLowerCaseInput.length() >= 4 && sLowerCaseInput.substring(0, 4).equals
 			}
 		}
 	}
+
+
+
+	/**
+	 * Diese Methode gibt Fehlermeldungen in der Konsole aus.
+	 * 
+	 * @param psPrefix			Text, welcher vor der Fehlermeldung angezeigt werden soll.
+	 * @param pnErrorMessage	Fehlermeldung.
+	 * @param psSuffix			Text, welcher nach der Fehlermeldung angezeigt werden soll.
+	 */
+	private static void printErrorMessage(String psPrefix, int pnErrorMessage, String psSuffix) {
+		System.out.print(psPrefix); //Prefix ausgeben.
+
+		//Fehlermeldung ausgeben:
+		if (pnErrorMessage == ReturnValueTypes.SUCCESS) {
+			System.out.print("Success");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN) {
+			System.out.print("Unknown");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_DIVIDE_BY_ZERO) {
+			System.out.print("Cannot divide by zero");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNEQUAL_DATA) {
+			System.out.print("Operands are of different type");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_SYNTAX) {
+			System.out.print("Syntax");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN_OPERATOR) {
+			System.out.print("Unknown operator");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN_IDENTIFIER) {
+			System.out.print("Unknown identifier");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_NOT_ENOUGH_OPERANDS) {
+			System.out.print("The operation needs more operands");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_CANNOT_OFFSET_STRING_TO_NUMBER) {
+			System.out.print("Cannot offset String to number");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN_TOKEN) {
+			System.out.print("Encountered unknown token.");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN_KEYWORD) {
+			System.out.print("Encountered onknown keyword");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_VARIABLE_NAME_DOES_EXIST) {
+			System.out.print("Variable name does already exist");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_FILE_DOES_NOT_EXIST) {
+			System.out.print("File does not exist");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_FILE_CANNOT_BE_READ) {
+			System.out.print("Cannot read file");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_NO_MAIN_FUNCTION) {
+			System.out.print("Main function is missing");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_MAIN_FUNCTION_HAS_PARAMETER) {
+			System.out.print("Main function has too many parameters");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_INCORRECT_PARAMETER_NUMBER) {
+			System.out.print("Function call has an incorrect number of arguments");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_NO_RETURN_VALUE) {
+			System.out.print("Non-existing return value was expected");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_INSTANCE_NAME_DOES_EXIST) {
+			System.out.print("The name of an instance is already used");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_INSTANCE_NAME_CANNOT_BE_CLASS_NAME) {
+			System.out.print("Instance name cannot be class name");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_UNKNOWN_CLASS) {
+			System.out.print("Unknown class type");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_STACK_OVERFLOW) {
+			System.out.print("StackOverflow");
+		}
+		else if (pnErrorMessage == ReturnValueTypes.ERROR_FUNCTION_NAME_IS_IDENTICAL) {
+			System.out.println("Multiple functions are defined with the same name");
+		}
+		else {
+			System.out.print("unknwon error occured. Error message: " + pnErrorMessage);
+		}
+
+		System.out.println(psSuffix); //Suffix ausgeben.
+	}
 }

src/errorHandling/ReturnValueTypes.java

@@ -155,4 +155,14 @@ public class ReturnValueTypes {
 	 * Speichert die Fehlermeldung fuer ein unbekanntes Steuerzeichen.
 	 */
 	public static int ERROR_UNKNOWN_CTRL_CHAR = 24;
+
+	/**
+	 * Speichert die Fehlermeldung fuer einen Funktionsnamen, der mehrmals vorkommt.
+	 */
+	public static int ERROR_FUNCTION_NAME_IS_IDENTICAL = 25;
+
+	/**
+	 * Speichert die Fehlermeldung fuer import-Schluesselwoerter, die einen StackOverflow erzeugen.
+	 */
+	public static int ERROR_IMPORT_STACK_OVERFLOW = 26;
 }

src/fileScanner/FileScanner.java

@@ -52,7 +52,7 @@ else if (!fileObj.canRead()) {
 			sFileContent = Files.readString(filePathObj);
 		}
 		catch (IOException e){
-			e.printStackTrace();
+			return new ReturnValue<LinkedList<String>>(null, ReturnValueTypes.ERROR_FILE_CANNOT_BE_READ);
 		}
 
 		//Inhalt der Datei in einzelne Lisp-Ausdruecke unterteilen:
@@ -61,9 +61,8 @@ else if (!fileObj.canRead()) {
 		int nBracketsClosed = 0; //Speichert die Anzahl an geschlossenen Klammern.
 		int nBracketsOpened = 0; //Speichert die Anzahl an geoeffneten Klammern.
 
-		//Zeilenumbrueche und Tabulatoren aus dem Quellcode entfernen, da diese den Tokenizer verwirren:
+		//Tabulatoren aus dem Quellcode entfernen, da diese den Tokenizer verwirren:
 		sFileContent = sFileContent.replaceAll("\t", "");
-		sFileContent = sFileContent.replaceAll("\n", "");
 		sFileContent = sFileContent.replaceAll("\r", "");
 
 		//Quellcode zeichenweise durchlaufen um diesen in Ausdruecke zu unterteilen:
@@ -79,11 +78,19 @@ else if (chCurrentCharacter == ')') {
 				nBracketsClosed++;
 			}
 
+			if (chCurrentCharacter == ';') {
+				//Es wurde ein Kommentar gefunden -> Kommentar wird entfernt:
+				while (!sFileContent.isEmpty() && sFileContent.charAt(0) != '\n') {
+					sFileContent = sFileContent.substring(1);
+				}
+				continue;
+			}
+
 			sCurrentExpression += chCurrentCharacter; //Aktuelles Zeichen dem aktuellen Ausdruck anfuegen.
 
 			if ((nBracketsOpened != 0 && nBracketsClosed != 0) && (nBracketsOpened == nBracketsClosed)) {
 				//Es wurden gleich viele Klammern geoeffnet und geschlossen:
-				lsSourceCode.add(sCurrentExpression);
+				lsSourceCode.add(sCurrentExpression.replaceAll("\n", "")); //Zeilenumbruecke entfernen.
 				sCurrentExpression = "";
 				nBracketsClosed = 0;
 				nBracketsOpened = 0;