Method parse

examples/block3.rs:118–128

(mut self)

    }

    fn parse(mut self) -> Option<Chain> {
        let mut elements = vec![];
        while let Some(e) = self.parse_next() {
            elements.push(e);
        }
        if !elements.is_empty() {
            Some(Chain { elements })
        } else {
            None
        }
    }

    fn parse_next(&mut self) -> Option<Element> {
        let next = self.tokens.get(self.current).map(|s| s.to_string());