flatten (Node 3 (Node 5 Nil Nil) (Node 7 Nil Nil)) Infix == [5,3,7]
flatten (Node 3 (Node 5 Nil Nil) (Node 7 Nil Nil)) GspInfix == [7,3,5]

topspiegel Leaf 'a' == Leaf 'a'
topspiegel (BNode 5 (Leaf 'a' Leaf 'b')) == (BNode 5 (Leaf 'b' Leaf 'a'))

spiegel Leaf 'a' == Leaf 'a'
spiegel (BNode 5 (BNode 7 Leaf 'a' Leaf 'b') (BNode 9 Leaf 'c' Leaf 'd'))) == (BNode 5 (BNode 9 Leaf 'd' Leaf 'c') (BNode 7 Leaf 'b' Leaf 'a')))

wege (GNode 1 [2,3,4] Empty) 2 3 == False
wege (GNode 1 [2,3,4] (GNode 2 [3] Empty)) 2 3 == True