gistfile2.txt

TestGpp.groovy

//
// Actually, its filename is Test.gpp
//
class Test {

    static class Expr<T> {

    }
    static class Bin<T> extends Expr<T> {
        Expr<T> op1
        Expr<T> op2
    }
    static class Const<T> extends Expr<T> {
        T val
    }
    static class Plus<T> extends Bin<T> {
    }
    static class Mult<T> extends Bin<T> {
    }

    @mixed static setup() {
        Integer.metaClass.plus = { Integer op ->
            Integer op1 = delegate
            Integer op2 = op
            new Plus<Integer>(op1: new Const<Integer>(val:op1), op2: new Const<Integer>(val:op2))
        }
        Integer.metaClass.multiply = { Integer op ->
            Integer op1 = delegate
            Integer op2 = op
            new Mult<Integer>(op1: new Const<Integer>(val:op1), op2: new Const<Integer>(val:op2))
        }
    }
    static match(Expr a, Expr b) {
        return [a.class, b.class]
    }
    static Expr optimize(Mult e) {
        if (match(e.op1, e.op2) == [Const, Const]) 
            return new Const<Integer>(val: (e.op1 as Const<Integer>).val * (e.op2 as Const<Integer>).val)
            if((e.op1 as Const).val == 1) return (e.op2 as Const) else
            if((e.op2 as Const).val == 1) return (e.op1 as Const)
    }
    @dynamic static void main(String[] args) {
        setup()
        def a = 1 * 2
        println optimize(a).val
    }
}