a one liner that is actually easy to understand, good one.

Is it for getting a negative sum, so that inject subtracts it based on that instead of writing it seperately?

In the ternary operator's else condition, what is the purpose of -d.to_i?
I understand the to_i part, its the -d that is throwing me off.

Any help on what ruby feature I should use to automatically call the next name and also will Argument error suffice for calling an error??

Correct me if I am wrong, but that is not said anywhere in the description.

Where a and b are strings is the expession if a > b same as if a.length > b.length