diff --git a/Tutorium/tut12/notes.md b/Tutorium/tut12/notes.md
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+# Notes for Tutorium 12 - 19.01.2024
+
+## Topics
+
+- Type Annotation - The Full Guide
+    - Basics
+        - parameter
+        - variable
+        - return type
+        - 
+    - Advanced
+        - Collections
+        - args, kwargs
+- Functional programming
+    - map
+    - filter
+    - reduce
+    - function composition
+    - monads - Result/Optional
+- Pattern-Matching
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diff --git a/Tutorium/tut12/src/functional.py b/Tutorium/tut12/src/functional.py
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+from typing import Callable, Iterable, Iterator
+
+type Optional[T] = T | None
+
+
+def map[T, R](func: Callable[[T], R], xs: Iterable[T]) -> Iterable[R]:
+    return [func(x) for x in xs]
+
+
+def filter[T](func: Callable[[T], bool], xs: Iterable[T]) -> Iterable[T]:
+    return [x for x in xs if func(x)]
+
+
+def reduce[T](func: Callable[[T, T], T], xs: Iterable[T]) -> T:
+    it: Iterator[T] = iter(xs)
+    value: T
+    try:
+        x: T = next(it)
+    except StopIteration:
+        raise TypeError("can't reduce empty list")
+    else:
+        value = x
+    for y in it:
+        value = func(value, y)
+    return value
+
+
+def compose[T](*funcs: Callable[[T], T]) -> Callable[[T], T]:
+    return reduce(lambda f, g: lambda n: f(g(n)), funcs)
+
+
+f: Callable[[int], int] = lambda n: n + 42
+g: Callable[[int], int] = lambda n: n ** 2
+h: Callable[[int], int] = lambda n: n - 3
+
+print(compose(f, g, h)(0))
+
+print(list(filter(lambda e: bool(e), [1, 2, 3, None, 5, 6])))
+print(list(filter(lambda e: not bool(e), [1, 2, 3, None, 5, 6])))
+
+print(list(map(lambda e: str(e), [1, 2, 3, 4, 5, 6, "hello_functional"])))
+
+print(list(
+    filter(lambda e: len(e) > 1,
+           map(lambda e: str(e),
+               [1, 2, 3, 4, "hello_world"]))))
+
+print(list(filter(lambda e: isinstance(e, int), [1, 2, 3, "hello"])))