Get writes to the channel combinations (n, m) out is here for writing the combinations as soon as they are available it overwrites a previous returned combination, so the caller needs to copy it if it wants to store it we close this channel to signal we are done it also has a Reply channel, so that the caller can tell us that it wants us to stop, by closing it.

NonDivisibleSubsetSlow returns the length of the longest subset of s, such that the sum of any two of its numbers is not divisible by d it is very slow, as it loops through s ( a potentially big list ), and it can end up calculating lots of subsets.