to_s - to_str, to_i - to_int, to_a - to_ary...

I don’t understand what’s the difference between to_s and to_str (the same for to_i – to_int, to_a – to_ary, and so), and why we need both method styles. I found it very confusing, against the KISS principle even. Can anybody explain it to me, please?

Thanks in advance.

The short forms (to_s, to_i, etc) say “do your best to give me a string/integer/... representation of the receiver). The to_str longer-form methods say instead that the receiver can effectively be viewed as a string, and ask for the string representation. So the short forms are permissive, and the long forms will give an error if no exact conversion exists.