Alejandro,
On 06 Feb 2015, at 15:10, Alejandro Infante <alejandroinfante91@gmail.com> wrote:
Hello, I have just found that calling asByteArray for any negative small integer returns the same result that the positive small integer. Is it supposed to be like that or is it a bug?
1 asByteArray = -1 asByteArray. "true"
(1 to: 100000) allSatisfy: [ :int | int asByteArray = int negated asByteArray ] âtrue"
Cheers, Alejandro
(These kinds of questions should be asked on pharo-users@lists.pharo.org) You can only represent positive numbers as ByteArrays, because to represent negative numbers you have to decide how to do that. The most common solution is to use 2-complement. To do this you also need to decide on the number of bytes to use. Here is an example using 4 bytes: | integer size mask | integer := -123. size := 4. mask := (2 raisedTo: size * 8) - 1. (mask bitAnd: ((integer abs bitXor: mask) + 1)) asByteArrayOfSize: 4. => #[255 255 255 133] => FF FF FF 85 The reverse is: | integer size mask | integer := #[255 255 255 133] asInteger. size := 4. mask := (2 raisedTo: size * 8) - 1. (mask bitAnd: ((integer abs bitXor: mask) + 1)) negated This is for negative numbers. Positive numbers need not be 2-complemented. When decoding, integers < (2 raisedTo: (size * 8) - 1) are negative. HTH, Sven