Clojure read-string [duplicate]

Question

(read-string "01") returns 1.

In fact read-string from "01" to "07" returns the correct answer. But while we do (read-string "08") it throws an error:

NumberFormatException Invalid number: 08 clojure.lang.LispReader.readNumber (LispReader.java:330).

Can anyone plese help me to figure out why?"

Answer 1

If the string starts with a 0, then the number is read as an octal number: https://www.ascii.cl/conversion.htm

Thus, the table below, with some sample conversions:

• 01 -> 1
• 02 -> 2
• 0117 -> 79
• 0200 -> 128
• 08 -> invalid

Answer 2

If you had kept going you may have seen:

> (read-string "010")
8

Literal numbers beginning with 0 are taken to be octal (base 8). Hence the digit 8 is not valid.