(@ search tree-root key .value +-
    (@ select-next tn bit +-
        ('// >
            [= 0] bit && [tn.left] / tn.left
        >
            [= 1] bit && [tn.right] / tn.right
        >
            (exit ERR_KEY_NOT_FOUND)
        )
    )

    (node.data .value -
        (# bits-in key (@ bit +-
                           (# select-next node bit .node)
                       )
        -
            (tree-root .node ..)
        )
    )
+
    {tree-node} tree-root
    {integer : 2^64} key
)
