public Expression getValueBySlot(int slot) {
		slot--; // skip this parameter (not an outer value)
		for (int i = 0; i < headCount; i++) {
			if (slot == 0) {
				Expression expr = head[i];
				if (i >= headMinCount)
					headMinCount = i;
				return expr;
			}
			slot -= head[i].getType().stackSize();
		}
		return null;
	}