|| is the OR operand. So if the first case passes (in this case i == 0), then it will skip trying to validate the second case (str[i-1] == ' ').

Since i is always 0 on the loop's initialization, then it will never try to validate str[i-1] == ' ' on the first pass

how doesn't str[i-1] throw an error in the first pass? does it skip it because of the ||?

the int conversion i think is unnessesary. in go division returns the same type and in integer case it returns the quotient