What is an Illegal octal digit?

Question

I'm trying to make an array of zip codes.

array = [07001, 07920]

This returns :

array = [07001, 07920]
                  ^
    from (irb):12
    from :0

Never seen this before. Any workarounds?

Answer 1

Ruby is interpreting numbers that have a leading 0 as being in octal (base 8). Thus the digits 8 and 9 are not valid.

It probably makes more sense to store ZIP codes as strings, instead of as numbers (to avoid having to pad with zeroes whenever you display it), as such: array = ["07001", "07920"]

Answer 2

Your array is of numbers, so the leading zero causes it to be interpreted as octal (valid digits 0-7). If these are zip codes, and the leading zero is significant, they should probably be strings.

Answer 3

Numbers that start with 0 are assumed to be in octal format, just like numbers that start with 0x are assumed to be in hexadecimal format. Octal digits only go from 0 to 7, so 9 is simply not legal in an octal number.

The easiest workaround would be to simply write the numbers in decimal format: 07001 in octal is the same as 3585 in decimal (I think). Or did you mean to write the numbers in decimal? Then, the easiest workaround is to leave off the leading zeroes: 07001 is the same as 7001 anyway.

However, you mention that you want an array of ZIP codes. In that case, the correct solution would be to use, well, an array of ZIP codes instead of an array of integers, since ZIP codes aren't integers, they are ZIP codes.