pub fn prev(&mut self) -> bool {
        if self.position == 0 {
            false
        } else {
            self.position -= 1;
            true
        }
    }
/// Goes back by one token in the stream. Returns whether the stream
/// actually went back. Note that it will not go back only if already at
/// position `0`.
Goes back by one token in the stream. Returns whether the stream
actually went back. Note that it will not go back only if already at
position `0`.
Goes back by one token in the stream . Returns whether the stream actually went back . Note that it will not go back only if already at position ` 0 ` .
pub fn prev(&mut self) -> bool {
        if self.position == 0 {
            false
        } else {
            self.position -= 1;
            true
        }
    }
pub fn prev ( & mut self ) -> bool { if self . position == 0 { false } else { self . position -= 1 ; true } }
Goes back by one token in the stream.
Goes back by one token in the stream .
&mut self
&mut self