I am experimenting with a script that utilizes negative 0. But negative zero seems to not work in scriptwiz. For example if I do this:
OP_0
OP_NEGATE
Scriptwiz shows me the ordinary zero, not a negated version. Also, if I try to express this sequence:
-1, -0, 0, 1
using their hex encodings, I try this:
<0x81>
<0x80>
<0x>
<0x01>
But I get this unexpected result:
-1 0x80 0 1
Negative zero is sometimes necessary when doing 32 bit binary addition in bitcoin script. For example, suppose you binary-add together 64 bits (treating them as two sets of 32 bits each) and you happen to get this result:
10000000000000000000000000000000
If, to save space on the stack, you roll that 32 bit number up into a 4 byte integer, everything after the leading bit is 0, but, because bitcoin script uses signed integers, it will interpret the leading 1 as a negator, resulting in -0. So I would want to store a negative 0 on the stack to represent these 32 bits. Similarly, if I want to take the representation -0 later in my script and "unpack" it into its constituent 32 bits, I need to know the sign of the 0 so that I can compute whether the leading bit should be a 1 or a 0.
It would be great if scriptwiz handled negative 0s properly so that I can use it to continue experimenting with 32 bit adders.
By the way, the reason I want 32 bit adders is because I am trying to implement a sha256 algorithm in bitcoin script that allows for checking if the hash of the input has a certain number of leading 0s. To do this on I need to implement the entirety of the sha256 algorithm in bitcoin script, and the algorithm uses 32 bit addition several times, and -- when experimenting with hashing an empty string in particular, which is a common test vector -- this requires rolling up 10000000000000000000000000000000 and representing it as negative 0.
I am experimenting with a script that utilizes negative 0. But negative zero seems to not work in scriptwiz. For example if I do this:
OP_0
OP_NEGATE
Scriptwiz shows me the ordinary zero, not a negated version. Also, if I try to express this sequence:
-1, -0, 0, 1using their hex encodings, I try this:
But I get this unexpected result:
-1 0x80 0 1Negative zero is sometimes necessary when doing 32 bit binary addition in bitcoin script. For example, suppose you binary-add together 64 bits (treating them as two sets of 32 bits each) and you happen to get this result:
10000000000000000000000000000000If, to save space on the stack, you roll that 32 bit number up into a 4 byte integer, everything after the leading bit is 0, but, because bitcoin script uses signed integers, it will interpret the leading 1 as a negator, resulting in -0. So I would want to store a negative 0 on the stack to represent these 32 bits. Similarly, if I want to take the representation -0 later in my script and "unpack" it into its constituent 32 bits, I need to know the sign of the 0 so that I can compute whether the leading bit should be a 1 or a 0.
It would be great if scriptwiz handled negative 0s properly so that I can use it to continue experimenting with 32 bit adders.
By the way, the reason I want 32 bit adders is because I am trying to implement a sha256 algorithm in bitcoin script that allows for checking if the hash of the input has a certain number of leading 0s. To do this on I need to implement the entirety of the sha256 algorithm in bitcoin script, and the algorithm uses 32 bit addition several times, and -- when experimenting with hashing an empty string in particular, which is a common test vector -- this requires rolling up 10000000000000000000000000000000 and representing it as negative 0.