>The submission is a tweet which doesn't really have a title, so the submitter was forced to make up one. Unfortunately the assertion in the chosen title is not correct. In Python the mod operator returns a number with the same sign as the second argument:
>Since its 1983 standard (Forth-83), Forth has implemented floored division as standard. Interestingly, almost all processor architectures natively implement symmetric division.
>What is the difference between the two types? In floored division, the quotient is truncated toward minus infinity (remember, this is integer division we’re talking about). In symmetric division, the quotient is truncated toward zero, which means that depending on the sign of the dividend, the quotient can be truncated in different directions. This is the source of its evil.
>I’ve thought about this a lot and have come to the conclusion that symmetric division should be considered harmful.
>There are two reasons that I think this: symmetric division yields results different from arithmetic right shifts (which floor), and both the quotient and remainder have singularities around zero.
>If you’re interested in the (gory) details, read on. [...]
>Python, unlike C, has the mod operator always return a positive number (twitter.com/id_aa_carmack):
https://news.ycombinator.com/item?id=29729890
https://twitter.com/ID_AA_Carmack/status/1476294133975240712
tzs on Dec 30, 2021 | next [–]
>The submission is a tweet which doesn't really have a title, so the submitter was forced to make up one. Unfortunately the assertion in the chosen title is not correct. In Python the mod operator returns a number with the same sign as the second argument:
https://news.ycombinator.com/item?id=29732335DonHopkins on Dec 30, 2021 | parent | context | favorite | on: Python, unlike C, has the mod operator always retu...
The FORTH-83 standard adopted floored division.
Signed Integer Division, by Robert L. Smith. Originally appearing in Dr. Dobb's Journal September 1983:
https://wiki.forth-ev.de/doku.php/projects:signed_integer_di...
Lots of other languages got it wrong:
https://en.wikipedia.org/wiki/Modulo_operation#In_programmin...
Symmetric division is the kind of thing that causes rockets ships to explode unexpectedly.
Symmetric division considered harmful:
https://www.nimblemachines.com/symmetric-division-considered...
>Since its 1983 standard (Forth-83), Forth has implemented floored division as standard. Interestingly, almost all processor architectures natively implement symmetric division.
>What is the difference between the two types? In floored division, the quotient is truncated toward minus infinity (remember, this is integer division we’re talking about). In symmetric division, the quotient is truncated toward zero, which means that depending on the sign of the dividend, the quotient can be truncated in different directions. This is the source of its evil.
>I’ve thought about this a lot and have come to the conclusion that symmetric division should be considered harmful.
>There are two reasons that I think this: symmetric division yields results different from arithmetic right shifts (which floor), and both the quotient and remainder have singularities around zero.
>If you’re interested in the (gory) details, read on. [...]