Mod function bug?

Scripting
1

Hello,

Unless I’m missing something, it seems the “mod” function is returning bogus results.
Discovered this when writing a converter for HSV to RGB. Didn’t work with the built in “mod” funciton. I wrote a custom “mod” function for the script and everything was OK.

Hope this helps.

Bruce

2

Hi Bruce,

What development language are you using? Do you have some sample code we can evaluate?

– Dale

3

Hello Dale,

I’m using the rhino enabled vb script (am currently coding in the editscript Rhino editor).

Any code with the mod function will do, for example 0.5 Mod 2 should equal 0.5, but Rhino is returning 0.

Option Explicit
'Script written by <insert name>
'Script copyrighted by <insert company name>
'Script version December 7, 2015 10:58:45 PM

Call Main()

Sub Main()
     Call Rhino.Print("0.5 Mod 2 = 0.5, but 0.5 Mod 2 =  " & 0.5 Mod 2 & " using Rhino Script.")
End Sub

Best regards,

Bruce

4

Hi Bruce,

VBScript’s Mod operator divides two integers and returns the integer remainder.

result = number1 Mod number2

If number1 or number2 are floating point numbers, they are first rounded to integers.

If you want to implement a modulus function that operates on floating point numbers, you’ll have to do the work yourself.

For example:

Function Modulo(a, b)
  Modulo = a - (b * (a \ b))
End Function

MsgBox Modulo(0.5, 2)
5

You can always use this:

http://4.rhino3d.com/5/rhinoscript/utility_methods/colorhsvtorgb.htm

7

@Dale, quite interesting to see integer division in vbscript and how this function compares to python using negative numbers :wink:

c,

8

Hello Dale,

Thank you. I guess I should have read the Mod function description more closely.

Best regards,

Bruce

9

For future reference, I’ve added a new Rhino.FMod function to the Rhino WIP which divides two floating-point numbers and returns the floating-point remainder. You should see this function in next week’s WIP release.

10

Hello Dale,

Thank you very kindly.

Best regards,

Bruce