diff --git a/code/Angabe5.hs b/code/Angabe5.hs
index b237dc3..cbac42c 100644
--- a/code/Angabe5.hs
+++ b/code/Angabe5.hs
@@ -27,14 +27,14 @@ class Eq a => Menge_von a where
 
    -- Protoimplementierungen
    leer = []
-   vereinige xs ys     = xs ++ ys
-   schneide xs ys      = xs \\ (xs \\ ys)
-   ziehe_ab xs ys      = xs \\ (intersectBy (==) xs ys)
-   ist_teilmenge xs ys = (length (ziehe_ab xs ys) == 0)
+   vereinige xs ys     = if (has_duplicates xs) || (has_duplicates ys) then error "Fehler" else clear_duplicates (xs ++ ys)
+   schneide xs ys      = if (has_duplicates xs) || (has_duplicates ys) then error "Fehler" else xs \\ (xs \\ ys)
+   ziehe_ab xs ys      = if (has_duplicates xs) || (has_duplicates ys) then error "Fehler" else xs \\ (intersectBy (==) xs ys)
+   ist_teilmenge xs ys = if (has_duplicates xs) || (has_duplicates ys) then error "Fehler" else (length (ziehe_ab xs ys) == 0)
    ist_obermenge xs ys = ist_teilmenge ys xs
    ist_element x xs    = anzahl x xs >= 1
    anzahl x xs         = if (has_duplicates xs) then error "Fehler" else (length . filter (== x)) xs
-   ist_leer xs         = xs == leer
+   ist_leer xs         = if (has_duplicates xs) then error "Fehler" else xs == leer
    sind_gleich xs ys   = ist_teilmenge xs ys && ist_teilmenge ys xs
 
 -- Weitere Typen:
@@ -163,13 +163,10 @@ build_pairs fkt arg
 -- Aufgabe A.3
 
 instance Menge_von Int where
-   vereinige xs ys     = clear_duplicates (xs ++ ys)
 
 instance Menge_von Zahlraum_0_10 where
-   vereinige xs ys     = clear_duplicates (xs ++ ys)
 
 instance Menge_von Funktion where
-   vereinige xs ys     = clear_duplicates (xs ++ ys)
 
 -- Aufgabe A.4
 
@@ -188,13 +185,25 @@ instance Show a => Show (ElemTyp a) where
 -- Aufgabe A.6
 
 instance Eq a => Menge_von (ElemTyp a) where
-   anzahl x xs = (length . filter (== x)) xs
+   anzahl x xs         = (length . filter (== x)) xs
+   vereinige xs ys     = xs ++ ys
+   schneide xs ys      = xs \\ (xs \\ ys)
+   ziehe_ab xs ys      = xs \\ (intersectBy (==) xs ys)
+   ist_teilmenge xs ys = (length (ziehe_ab xs ys) == 0)
+   ist_obermenge xs ys = ist_teilmenge ys xs
+   ist_leer xs         = xs == leer
 
 -- Aufgabe A.7
 
 instance (Eq a,Eq b,Eq c,Eq d,Eq e) => Menge_von (PH_ElemTyp a b c d e) where
-   vereinige xs ys     = clear_duplicates (xs ++ ys)
 
 -- Aufgabe A.8
 
 instance (Eq p,Eq q,Eq r) => Menge_von (PH_ElemTyp' p q r) where
+   anzahl x xs         = (length . filter (== x)) xs
+   vereinige xs ys     = xs ++ ys
+   schneide xs ys      = xs \\ (xs \\ ys)
+   ziehe_ab xs ys      = xs \\ (intersectBy (==) xs ys)
+   ist_teilmenge xs ys = (length (ziehe_ab xs ys) == 0)
+   ist_obermenge xs ys = ist_teilmenge ys xs
+   ist_leer xs         = xs == leer
\ No newline at end of file