topdown-rs 0.3.3

A top-down parsing library
Documentation 
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use super::{CharSeq, ParserResult, Parser, Succ, Fail, Error};

pub struct Chainr<'a, T, F> {
    term: &'a (Parser<T>+'a),
    operator: &'a (Parser<F>+'a),
    allow_trailing_operator: bool
}

pub fn chainr<'a, T, F>(p: &'a (Parser<T>+'a), o: &'a (Parser<F>+'a), a: bool) -> Chainr<'a, T, F> 
    where F: Fn(T, T) -> T {
    return Chainr{term: p, operator: o, allow_trailing_operator: a};
}

impl<'a, T, F> Parser<T> for Chainr<'a, T, F> where F: Fn(T, T) -> T {
    #[allow(unused_variables)]
    fn _parse(&self, cs: &mut CharSeq) -> ParserResult<T> {
        match cs.accept(self.term) {
            Succ(l) => {
                match cs.accept(self.operator) {
                    Succ(o) => match cs.accept(self) {
                        Succ(r) => return Succ(o.call((l, r))),
                        Fail(m, lo) => {
                            if self.allow_trailing_operator {
                                return Succ(l)
                            } else {
                                return Fail(m, lo)
                            }
                        },
                        Error(m, l) => return Error(m, l)
                    },
                    Fail(m, lo) => return Succ(l),
                    Error(m, lo) => return Succ(l),
                }
            },
            Fail(m, l) => return Fail(m, l),
            Error(m, l) => return Error(m, l)
        }
    }
}

#[cfg(test)]
#[allow(unused_variables)]
#[allow(unused_imports)]
mod tests {
    use super::chainr;
    use super::super::{CharSeq, re, ParserResult, Parser, Succ, Fail, Error};

    struct Op;

    impl<F> Parser<F> for Op where F: Fn(int, int) -> int {
        fn _parse(&self, cs: &mut CharSeq) -> ParserResult<F> {
            return cs.accept(&re("\\+|-"))
                .map(|o| {
                     return move |: a:int, b:int| {
                         if o.as_slice() == "+" {
                            return a+b;
                        } else {
                            return a-b;
                        }
                     }
                });
        }
    }

    struct Expr;

    impl Parser<int> for Expr {
        fn _parse(&self, cs: &mut CharSeq) -> ParserResult<int> {
            return cs.accept(&re("[1-9][0-9]*")).map(|x| x.as_slice().parse().unwrap());
        }
    }

    #[test]
    fn test_chainr1() {
        let mut cs = CharSeq::new("1-5", "<mem>");
        let term = Expr;
        let op = Op;
        let expr = chainr(&term, &op, false);
        match cs.accept(&expr) {
            Succ(c) => assert_eq!(c, -4),
            Fail(a, b) => assert!(false, "failed"),
            Error(a, b) => assert!(false, "error")
        }
    }


    #[test]
    fn test_chainr2() {
        let mut cs = CharSeq::new("1-5-6", "<mem>");
        let term = Expr;
        let op = Op;
        let expr = chainr(&term, &op, false);
        match cs.accept(&expr) {
            Succ(c) => assert_eq!(c, 2),
            Fail(a, b) => assert!(false, "failed"),
            Error(a, b) => assert!(false, "error")
        }
    }


    #[test]
    fn test_chainr3() {
        let mut cs = CharSeq::new("30+5-6+12", "<mem>");
        let term = Expr;
        let op = Op;
        let expr = chainr(&term, &op, false);
        match cs.accept(&expr) {
            Succ(c) => assert_eq!(c, 17),
            Fail(a, b) => assert!(false, "failed"),
            Error(a, b) => assert!(false, "error")
        }
    }


    #[test]
    fn test_chainr4() {
        let mut cs = CharSeq::new("30+5-", "<mem>");
        let term = Expr;
        let op = Op;
        let expr = chainr(&term, &op, true);
        match cs.accept(&expr) {
            Succ(c) => assert_eq!(c, 35),
            Fail(a, b) => assert!(false, "failed"),
            Error(a, b) => assert!(false, "error")
        }
    }
}