diff --git a/info4/kapitel-8/Interpreter/interpreter.py b/info4/kapitel-8/Interpreter/interpreter.py
new file mode 100644
index 0000000000000000000000000000000000000000..088afa1935209694b55fdd0e0583b695bd52757f
--- /dev/null
+++ b/info4/kapitel-8/Interpreter/interpreter.py
@@ -0,0 +1,106 @@
+import lexer
+
+loop_program = '''x1 := 2;
+x2 := 3;
+x3 := x2 + 0;
+LOOP x1 DO
+ x2 := x3 + 1;
+ x3 := x2 + 0
+END;
+x0 := x2 + 0'''
+
+
+def process_assignment(token_queue, position, value_list, forbidden_identifiers):
+ identifier_1 = token_queue[position].v
+ if identifier_1 in forbidden_identifiers:
+ raise Exception("Identifier " + identifier_1 + "ist bereits in Loop vorhanden und darf nicht verwendet werden.")
+ if not token_queue[position + 1].k == 'EQUALS':
+ raise SyntaxError(":= in Zuweisung erwartet.")
+
+ if identifier_1 in value_list:
+ value_1 = value_list.get(identifier_1)
+ else:
+ value_1 = 0
+
+ if token_queue[position + 2].k == 'NUMBER':
+ value_1 += int(token_queue[position + 2].v)
+ value_list.update({identifier_1: value_1})
+ return position+3, value_list
+
+ if not token_queue[position + 2].k == 'IDENTIFIER':
+ raise SyntaxError("IDENTIFIER in Zuweisung erwartet.")
+ identifier_2 = token_queue[position + 2].v
+ if identifier_2 in forbidden_identifiers:
+ raise Exception("Identifier " + identifier_2 + " ist bereits in Loop vorhanden und darf nicht verwendet werden.")
+
+ if identifier_2 in value_list:
+ value_2 = value_list.get(identifier_2)
+ else:
+ value_2 = 0
+
+ if not token_queue[position + 4].k == 'NUMBER':
+ raise SyntaxError("NUMBER in Zuweisung erwartet.")
+ if token_queue[position + 3].k == 'PLUS':
+ value_1 = value_2 + int(token_queue[position + 4].v)
+ elif token_queue[position + 3].k == 'MINUS':
+ value_1 = max(0, value_2 + token_queue[position + 4].v)
+ else:
+ raise SyntaxError("PLUS oder MINUS in Zuweisung erwartet.")
+ value_list.update({identifier_1: value_1})
+ return position + 5, value_list
+
+def process_loop(token_queue, position, value_list, forbidden_identifiers):
+ identifier_token = token_queue[position+1]
+ if not identifier_token.k == 'IDENTIFIER':
+ raise SyntaxError('IDENTIFIER in LOOP erwartet.')
+ if not token_queue[position+2].k == 'DO':
+ raise SyntaxError('DO in LOOP erwartet.')
+
+ number_of_loops = int(value_list.get(identifier_token.v))
+ saved_position = position + 3
+ forbidden_identifiers.append(identifier_token.v)
+ for index in range(number_of_loops):
+ position = saved_position
+ end_found = False
+ while(not end_found):
+ position, value_list = process_program(token_queue, position, value_list, forbidden_identifiers)
+ if token_queue[position].k == 'SEMICOLON':
+ position = position + 1
+ continue
+ elif token_queue[position].k == 'END':
+ end_found = True
+ else: raise SyntaxError("SEMICOLON oder END erwartet.")
+ return position+1, value_list
+
+def process_program(token_queue, position, value_list, forbidden_identifiers):
+ current_key = token_queue[position].k
+ if current_key == 'IDENTIFIER':
+ try:
+ current_position, values = process_assignment(token_queue, position, value_list, forbidden_identifiers)
+ except IndexError:
+ raise Exception("Frühzeitiges Ende einer Zuweisung.")
+ elif current_key == 'LOOP':
+ try:
+ current_position, values = process_loop(token_queue, position, value_list, forbidden_identifiers)
+ except IndexError:
+ raise Exception("Frühzeitiges Ende eines LOOPs")
+ else:
+ raise SyntaxError("Keine passende Anweisung gefunden")
+ return current_position, values
+
+def interpret(program):
+ tokens = lexer.tokenize(program)
+ current_position = 0
+ values = {}
+ forbidden_identifiers = []
+ while current_position < len(tokens):
+ current_position, values = process_program(tokens, current_position, values, forbidden_identifiers)
+ if current_position < len(tokens) and not tokens[current_position].k == 'SEMICOLON':
+ raise SyntaxError("Semicolon erwartet")
+ else:
+ current_position = current_position + 1
+ if "x0" in values:
+ return values.get("x0")
+ return 0
+
+print(interpret(loop_program))
diff --git a/info4/kapitel-8/Interpreter/lexer.py b/info4/kapitel-8/Interpreter/lexer.py
new file mode 100644
index 0000000000000000000000000000000000000000..f6eb7a89b19a1cacccd114ec0a3ab7d3cbe9cea7
--- /dev/null
+++ b/info4/kapitel-8/Interpreter/lexer.py
@@ -0,0 +1,34 @@
+import re
+
+class Token:
+ def __init__(self, key, value):
+ self.k = key
+ self.v = value
+
+
+def tokenize(program):
+ token_queue = []
+ regex_to_token = [(re.compile(r'\d+'), 'NUMBER'),
+ (re.compile(r'x\d+'), 'IDENTIFIER'),
+ (re.compile(r'\+'), 'PLUS'),
+ (re.compile(r'-'), 'MINUS'),
+ (re.compile(r':='), 'EQUALS'),
+ (re.compile(r'LOOP'), 'LOOP'),
+ (re.compile(r'DO'), 'DO'),
+ (re.compile(r'END'), 'END'),
+ (re.compile(r';'), 'SEMICOLON'),
+ (re.compile(r'\s+'), 'WHITESPACE')]
+ current_position = 0
+ new_position = 0
+ while current_position < len(program):
+ for pattern, value in regex_to_token:
+ match = pattern.match(program, current_position)
+ if match:
+ if not value == 'WHITESPACE':
+ token_queue.append(Token(value, match.group()))
+ new_position = match.span()[1]
+ break
+ if current_position == new_position:
+ raise SyntaxError('Syntax Error in line: ' + str(program.count("\n", 0, current_position) + 1))
+ current_position = new_position
+ return token_queue
diff --git a/info4/kapitel-8/LOOP-Programme.ipynb b/info4/kapitel-8/LOOP-Programme.ipynb
new file mode 100644
index 0000000000000000000000000000000000000000..3e401844f4b6a3e2068720b95023bacfb4ddf01e
--- /dev/null
+++ b/info4/kapitel-8/LOOP-Programme.ipynb
@@ -0,0 +1,79 @@
+{
+ "cells": [
+ {
+ "cell_type": "code",
+ "execution_count": 1,
+ "metadata": {},
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "HI\n"
+ ]
+ },
+ {
+ "ename": "SyntaxError",
+ "evalue": "Syntax Error in line: 4 (<string>)",
+ "output_type": "error",
+ "traceback": [
+ "\u001b[0;36m File \u001b[0;32m\"<string>\"\u001b[0;36m, line \u001b[0;32munknown\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m Syntax Error in line: 4\n"
+ ]
+ }
+ ],
+ "source": [
+ "%run Interpreter/lexer.py"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 2,
+ "metadata": {},
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "HI\n"
+ ]
+ },
+ {
+ "ename": "SyntaxError",
+ "evalue": "Syntax Error in line: 1 (<string>)",
+ "output_type": "error",
+ "traceback": [
+ "Traceback \u001b[0;36m(most recent call last)\u001b[0m:\n",
+ " File \u001b[1;32m\"/usr/lib/python3.8/site-packages/IPython/core/interactiveshell.py\"\u001b[0m, line \u001b[1;32m3418\u001b[0m, in \u001b[1;35mrun_code\u001b[0m\n exec(code_obj, self.user_global_ns, self.user_ns)\n",
+ " File \u001b[1;32m\"<ipython-input-2-93cfbd622072>\"\u001b[0m, line \u001b[1;32m1\u001b[0m, in \u001b[1;35m<module>\u001b[0m\n tokenize(\"LOOP x1 DO P END\")\n",
+ "\u001b[0;36m File \u001b[0;32m\"/home/christopher/uni/Projektarbeit/prob-teaching-notebooks/info4/kapitel-8/Interpreter/lexer.py\"\u001b[0;36m, line \u001b[0;32m43\u001b[0;36m, in \u001b[0;35mtokenize\u001b[0;36m\u001b[0m\n\u001b[0;31m raise SyntaxError('Syntax Error in line: ' + str(program.count(\"\\n\", 0, current_position) + 1))\u001b[0m\n",
+ "\u001b[0;36m File \u001b[0;32m\"<string>\"\u001b[0;36m, line \u001b[0;32munknown\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m Syntax Error in line: 1\n"
+ ]
+ }
+ ],
+ "source": [
+ "tokenize(\"LOOP x1 DO P END\")"
+ ]
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Python 3",
+ "language": "python",
+ "name": "python3"
+ },
+ "language_info": {
+ "codemirror_mode": {
+ "name": "ipython",
+ "version": 3
+ },
+ "file_extension": ".py",
+ "mimetype": "text/x-python",
+ "name": "python",
+ "nbconvert_exporter": "python",
+ "pygments_lexer": "ipython3",
+ "version": "3.8.6"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}