import run_tests
from r3_itree import T, Tree

def preorder( tree: Optional[ Tree[ T ] ] ) \
        -> Generator[ T, None, None ]:
    if tree is not None:
        yield tree.value
        yield from preorder( tree.left )
        yield from preorder( tree.right )

def inorder( tree: Optional[ Tree[ T ] ] ) \
        -> Generator[ T, None, None ]:
    if tree is not None:
        yield from inorder( tree.left )
        yield tree.value
        yield from inorder( tree.right )

def postorder( tree: Optional[ Tree[ T ] ] ) \
        -> Generator[ T, None, None ]:
    if tree is not None:
        yield from postorder( tree.left )
        yield from postorder( tree.right )
        yield tree.value