fn pop(&mut self) -> Result<Value> {
        match self.stack.pop() {
            Some(v) => Ok(v),
            None    => self.error(ErrorCode::StackUnderflow)
        }
    }
// Pop the stack top item.
Pop the stack top item.
Pop the stack top item .
fn pop(&mut self) -> Result<Value> {
        match self.stack.pop() {
            Some(v) => Ok(v),
            None    => self.error(ErrorCode::StackUnderflow)
        }
    }
fn pop ( & mut self ) -> Result < Value > { match self . stack . pop ( ) { Some ( v ) => Ok ( v ) , None => self . error ( ErrorCode :: StackUnderflow ) } }
Pop the stack top item.
Pop the stack top item .
&mut self
&mut self