gistfile1.rs

struct Car {
    color: ~str,
    miles: int,
}
impl Car {
    fn new() -> ~Car { ~Car{color: ~"none", miles: 0,} }
}
macro_rules! simple_eq(( $ T : ident -> $ l : ident , $ r : expr ) =>
                       (
                       { let temp = $ T :: new ( ) ; & temp . $ l == & temp .
                       $ l ; fmt ! ( "%s == %s" , stringify ! ( $ l ) , $ r )
                       } ) ;)
macro_rules! simple_neq(( $ T : ident -> $ l : ident , $ r : expr ) =>
                        (
                        { let temp = $ T :: new ( ) ; & temp . $ l == & temp .
                        $ l ; fmt ! ( "%s != %s" , stringify ! ( $ l ) , $ r )
                        } ) ;)
pub struct Query {
    filters: ~[~str],
}
impl Query {
    fn new() -> Query { Query{filters: ~[],} }
    fn Where(self, new_filter: ~str) -> Query {
        let mut self = self;
        self.filters.push(new_filter);
        self
    }
    fn Execute() -> int {
        // return row_count for now
        0
    }
    fn ToString(&self) -> ~str {
        use core::str::{append};
        if self.filters.len() > 0 {
            let res = append(~"SELECT FROM [FIX] WHERE ",self.filters[0]);
            do self.filters.slice(1,self.filters.len()).foldr(res) |q,s| {
                append(append(s, " AND "),*q)
            }
        } else {
            ~"SELECT FROM [FIX]"
        }
    }
}
fn main() {
    let mut cars = Query::new();
    let mut res =
        cars.Where(simple_eq!(Car -> color ,
                              "red")).Where(simple_neq!(Car -> color ,
                                                        "blue")).ToString();
    io::println(res);
}