void slab() throws ScriptException {
		// token has ondefault1
		if (statement[1].tok == Token.integer) {
			int percent = statement[1].intValue;
			if (percent < 0 || percent > 100)
				numberOutOfRange(0, 100);
			viewer.slabToPercent(percent);
			return;
		}
		switch (statement[1].tok) {
		case Token.on:
			viewer.setBooleanProperty("slabEnabled", true);
			break;
		case Token.off:
			viewer.setBooleanProperty("slabEnabled", false);
			break;
		default:
			booleanOrPercentExpected();
		}
	}