added tut11 notes

Tutorium/tut12/src/functional.py

@@ -1,7 +1,5 @@
-from typing import Callable, Iterable, Iterator
-
-type Optional[T] = T | None
-
+from typing import Any, Callable, Iterable, Iterator
+    
 
 def map[T, R](func: Callable[[T], R], xs: Iterable[T]) -> Iterable[R]:
     return [func(x) for x in xs]
@@ -13,17 +11,25 @@ def filter[T](func: Callable[[T], bool], xs: Iterable[T]) -> Iterable[T]:
 
 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:
+    value: T | None = None
+    for x in it:
+        match value:
+            case None:
+                value = x
+            case _:
+                value = func(value, x)
+    if not value:
         raise TypeError("can't reduce empty list")
-    else:
-        value = x
-    for y in it:
-        value = func(value, y)
     return value
 
+def flatten(xs: Iterable[Any]) -> Iterable[Any]:
+    new_list = []
+    for s in xs:
+        if isinstance(s, Iterable):
+            new_list.append(flatten(s))
+        else:
+            new_list.append([s])
+    return new_list
 
 def compose[T](*funcs: Callable[[T], T]) -> Callable[[T], T]:
     return reduce(lambda f, g: lambda n: f(g(n)), funcs)
@@ -46,3 +52,4 @@ print(list(
                [1, 2, 3, 4, "hello_world"]))))
 
 print(list(filter(lambda e: isinstance(e, int), [1, 2, 3, "hello"])))
+print(list(flatten([[1, 2, 3], 4, [[5, 6], 7, [8, 9]]])))