private static void writeOperator(Writer output,
			AuOperator.Descriptor desc) throws IOException {
		if(desc == IntArithmetic.intAdd) {
			output.write("ia");
		}else if(desc == Products.productType) {
			output.write("prt");
		}else if(desc == Products.product) {
			output.write("prv");
		}else if(desc instanceof Lists.List) {
			Lists.List list = (Lists.List)desc;
			output.write("l");
			output.write(Integer.toString(list.getLength()));
		}else if(desc == Anys.any) {
			output.write("ayv");
		}else if(desc == Mutation.mutatorType) {
			output.write("mut");
		}else if(desc == Io.print) {
			output.write("iop");
		}else throw new RuntimeException("Unsupported operator " + desc);
	}