pub fn height(&self) -> i8 {
        match self.0 {
            Some(ref t) => t.h,
            None => 0,
        }
    }
// get height of BinTree, 0 if None
get height of BinTree, 0 if None
get height of BinTree 0 if None
pub fn height(&self) -> i8 {
        match self.0 {
            Some(ref t) => t.h,
            None => 0,
        }
    }
pub fn height ( & self ) -> i8 { match self . 0 { Some ( ref t ) => t . h , None => 0 , } }
get height of BinTree, 0 if None
get height of BinTree 0 if None
&self
&self