Intop strange result

What's wrong with intop?

strcpy $0 007
intop $0 $0 + 1
messagebox mb_ok $0

returns correctly 8

strcpy $0 008
intop $0 $0 + 1
messagebox mb_ok $0

returns incorrectly 1, when I should expect 9

If you attach a "0" before the number, it is going to be an octal number (a numbering system based on using digits 0-7). If you want to calculate using the decimal system, you have to remove the extra 0's before the number.

You can also use Math plug-in for calculations, but it doesn't support octal numbers (comes with NSIS).

this happens only if I attach 2 zero... If I use only one zero, it uses the decimal system?

Yeah, it has to have 2 0's before the number, which contradicts with the octal numbers definition in the docs in which those are "numbers beginning with a 0 and no x". But at the same time, the number 008 does not exist (like 009), and it is considered 0 because it is not valid.

Remember that IntOp always returns the result as a decimal number, so 007+001=8.

Yeah, it has to have 2 0's before the number, which contradicts with the octal numbers definition in the docs in which those are "numbers beginning with a 0 and no x".

Actually, it only needs 2 0's for numbers 0-7, because 010 = 8 (correct).

You don't really need two zeros. You just need the first digit after the zero to be in a valid range. That is, it must be larger or equal to 0 and smaller or equal to 7. If it's not in that range, it'll fall back to decimal.

So, the number 008 is considered in octal notation, because the first number after the initial zero is another 0 (which is in the correct "range"), but when it checks the entire number, it finds an invalid number (008) and replaces it with a 0. Am I right?

Correct.