Avoiding infinity in pow and /
Taking 0 to the power of any negative exponent equals infinity. In Max, this yields the unique float value inf. In cases where you want to avoid getting inf, and would prefer to get 0, you can simply make a special case for a 0 input, and pass it on directly, avoiding the pow object. On the left is an example of how to use routepass to force Max to output 0 when it would otherwise calculate infinity, such as when using a pow -1 object.
The same thing can happen when you divide a number by 0, the result of which is mathematically undefined. In Max, this yields the unique float value nan (not a number) or inf. In cases where you may encounter a division by 0 and wish to avoid the nan result, you can use sel to look for and prohibit sending the value 0 into the right inlet of the / object.
The /! object does this sort of protection automatically. If you try to divide by 0, it will send out 0. instead of inf.