Replicate C# Math.IEEERemainder in Lua?

Question

I am trying to replicate the behavior of Math.IEEERemainder (in C#) in Lua. I know that I can always write the entire thing from scratch, but I am trying to avoid it if there is something built-in.

I have tried the % operator and math.fmod. None of them behave the same.

For instance:

Math.IEEERemainder(3.0,2.0) //-1
(3.0%2.0) --1
math.fmod(3.0,2.0) --1

score 1 · Accepted Answer · answered Nov 07 '18 at 08:50

1

function IEEERemainder(x, y)
   y = y + 0.0
   local q1 = math.floor(x/y)
   local q2 = math.ceil(x/y)
   local r1 = x - y * q1
   local r2 = x - y * q2
   local d1 = math.abs(r1)
   local d2 = math.abs(r2)
   local r = (d1 < d2 or d1 == d2 and q1 % 2 == 0) and r1 or r2
   return r == 0 and x < 0 and -r or r
end

answered Nov 07 '18 at 08:50

Egor Skriptunoff

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Got it, so I guess LUA does not have one built-in, thanks a lot! – RandomGuy42 Nov 08 '18 at 00:47
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@nxgtrturbo - Where this function might be useful? I have no idea :-) – Egor Skriptunoff Nov 08 '18 at 07:19
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For very specific cases, see here: https://stackoverflow.com/questions/26671975/why-do-we-need-ieee-754-remainder/27378075#27378075 – RandomGuy42 Nov 09 '18 at 01:31
@nxgtrturbo - Thanks. Indeed, sin(x) would be better calculated using `IEEERemainder(x, 2*pi)` than `fmod(x, 2*pi)` – Egor Skriptunoff Nov 09 '18 at 07:37

Replicate C# Math.IEEERemainder in Lua?

1 Answers1