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- Subject: Re: Modulo operator produces incorrect results with negative operand(s).
- From: "Soni L." <fakedme@...>
- Date: Tue, 24 Jan 2017 23:46:31 -0200
On 24/01/17 09:47 PM, Milo Christiansen wrote:
etc all return -3 in this case?
Personally I think it's a bug, as "2" is not the correct result for
that expression (in any language but Lua it seems).
Don't top post. And read this:
(That's from the LuaRocks developer, I think. So they kinda know what
And check mailing list archives. This isn't the first time this has come up.
On Tue, Jan 24, 2017 at 6:40 PM, Soni L. <email@example.com
On 24/01/17 09:21 PM, Milo Christiansen wrote:
In Lua 5.3 "-3%5 == 2", according to my programmers calculator
and several other programing languages I tried this expression
in, the real result is -3.
On the other hand "5%-3 == 2", so maybe the result is correct,
and the bug is simply reversed operands if one is negative?
I discovered this because I am adding tests (based on the
official Lua tests) to my Go Lua VM, and one of the tests
failed because the incorrect result is coded into the test.
First of all your modulo is not my modulo (or at least this was a
thing back in C89... looks like it isn't in C99+).
Secondly, -3%5 == 2 because floor(-3/5) = -1, and (-1)*5+2 = -5+2
etc. This is an endless argument.
Thirdly, in case you're still reading this for some unknown
reason, RTFM always applies:
"Modulo is defined as the remainder of a division that rounds the
quotient towards minus infinity (floor division)."
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