pub fn pop(&mut self) -> Result<Data, StackErr> {
        match self.data.pop() {
            Some(d) => Ok(d),
            None => Err(StackErr::Underflow),
        }
    }
/// Pops an item off the stack.
Pops an item off the stack.
Pops an item off the stack .
pub fn pop(&mut self) -> Result<Data, StackErr> {
        match self.data.pop() {
            Some(d) => Ok(d),
            None => Err(StackErr::Underflow),
        }
    }
pub fn pop ( & mut self ) -> Result < Data , StackErr > { match self . data . pop ( ) { Some ( d ) => Ok ( d ) , None => Err ( StackErr :: Underflow ) , } }
Pops an item off the stack.
Pops an item off the stack .
&mut self
&mut self