Create Ranged Int Types w/macro

make_range_int_type

#![feature(macro_rules)]

//tested on:
//rustc 0.10
//host: x86_64-unknown-linux-gnu


use std::to_str::ToStr;

macro_rules! make_range_int_type(
    ($RangedIntName:ident $RIN:ident $OORN:ident $l:expr $u:expr) => (

        #[deriving(Show)]
        enum $RangedIntName {
            $OORN,
            $RIN(int)
        }

        impl Add<$RangedIntName, $RangedIntName> for $RangedIntName {
            fn add(&self, _rhs: &$RangedIntName) -> $RangedIntName {
                match (*self, *_rhs) {
                           ($RIN(x),$RIN(y)) => {
                               let value = x + y;
                               if $RangedIntName::is_in_range(value) { $RIN(value) } else { $OORN }
                           },
                           ($OORN, _) => $OORN,
                           (_, $OORN) => $OORN
                }
            }
        }

        impl $RangedIntName {
             fn from_int(i: int) -> $RangedIntName {
                if $RangedIntName::is_in_range(i) { $RIN(i) } else { $OORN }
            }

            fn is_in_range(i: int) -> bool {
                i>=$l && i <= $u
            }

            fn unwrap(self) -> int {
                    match self {
                        $RIN(x) => x,
                        $OORN => fail!("failed to unwrap $RangedIntName - OutOfRange!")
                    }
            }
        }

    );
)

make_range_int_type!(RangedIntNFiveToFive RINFiveToFive OutOfRangeNFiveToFive -5 5)

fn main() {
    let i = RangedIntNFiveToFive::from_int(1) + RangedIntNFiveToFive::from_int(-1) ;
    let j = RangedIntNFiveToFive::from_int(20) + RangedIntNFiveToFive::from_int(-22) ;
    let k = RangedIntNFiveToFive::from_int(1) + RangedIntNFiveToFive::from_int(-1);
    let l = RangedIntNFiveToFive::from_int(1).unwrap();
    println!("i: {}", i.to_str());                              //prints "i: RINFiveToFive(0)"
    println!("j: {}", j.to_str());                              //prints "j: OutOfRangeNFiveToFive"
    println!("k: {}", k.to_str());                              //prints "k: RINFiveToFive(0)"
    println!("l: {}", l.to_str());                              //prints "l: 1"

    let m = RangedIntNFiveToFive::from_int(20).unwrap();        //causes exit:"task '<main>' failed at 'failed to unwrap $RangedIntName - OutOfRange!', ranged_num.rs:47"
    println!("m: {}", m.to_str());                              //never reached
}