/sci/ - Science & Math

[Anonymous No.6756608]

Can someone explain why when I do 4/3 mod 1 I get 1/3, but when I do -4/3 mod 1 I get 2/3? I was looking some work over on google, and got these two results back.

[Anonymous No.6756633]

"mod 1" means that 1 is equivalent to zero.
4/3 can be written as "1 + 1/3."
1 is equivalent to zero, so 4/3 becomes "0 + 1/3," or just "1/3."
-4/3 can be written as "-1 - 1/3" which becomes "-0 - 1/3" or just "-1/3."
But 1 is equivalent to zero, so "-1/3" is like "0 - 1/3" which is "1 - 1/3" which is "2/3"

[fox No.6756817]

>>6756608
"mod" is loosely defined and its behavior can vary from one compiler to another.

Compare the division algorithms in this short paper:

http://research.microsoft.com/pubs/151917/divmodnote-letter.pdf

[Anonymous No.6757021]

>>6756817
It has nothing to do with the behavior of the implementation. Like >>6756633 pointed out, 4/3 = 1/3 (mod 1) which is NOT congruent to 2/3 (mod 1). As long as your calculator is not in error, you will never get 4/3 = 2/3 (mod 1) or -4/3 = 1/3 (mod 1), because that would be wrong.

[Anonymous No.6757045]