Can someone explain Math.fmod() vs using a % operator?

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Jonathan asked Dec 1, '20 Joerg Vogel edited Dec 1, '20

Can someone explain Math.fmod() vs using a % operator?

Working on a decision point in Flexscript I wanted to use a modulo math operator like I can within Excel. I started tinkering with this:

if (current.labels.assert("roundRobinVal", 1).value % 2) == 0) {...then do stuff...}

But no matter what I did the % did not seem to behave like I anticipated.

I then found Math.fmod() and made this:

if (Math.fmod(current.labels.assert("roundRobinVal", 1).value, 2) == 0) {...then do stuff...}

and it worked perfectly.

I am incrementing the roundRobinVal after the if().

I also don't understand the ", 1" in the latter portion of the .assert().

Software Version:

FlexSim 20.2.3

flexscript flexsim 20.2.3 math fmod

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Answer 1 · 2020-12-01T17:38:44Z

Matthew Gillespie answered Dec 1, '20

The F in fmod stands for float and doesn't round to the nearest integer like % does, for example:

3.4 % 2                  //    1
Math.fmod(3.4, 2)        //    1.4

· 1

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Jonathan commented · Dec 01, 2020 at 05:42 PM

That makes sense with some of the behavior I was seeing. I had been wondering if it was something like that.

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Answer 2 · 2020-12-01T15:28:43Z

Jason Lightfoot answered Dec 1, '20 Jason Lightfoot commented Dec 1, '20

The 1 is the initial value of the label in the assert -so the value it will take if it didn't exist.

The % operator should work exactly as fmod - can you post an example?

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Jonathan commented · Dec 01, 2020 at 03:32 PM

This works like I intended:

if (Math.fmod(current.labels.assert("roundRobinVal", 1).value, 2) == 0)

{newDest = current.outObjects[1];}

else

{newDest = current.outObjects[2];}

current.labels.assert("roundRobinVal", 1).value++;

This did not:

if ((current.labels.assert("roundRobinVal", 1).value % 2) == 0)

{newDest = current.outObjects[1];}

else

{newDest = current.outObjects[2];}

current.labels.assert("roundRobinVal", 1).value++;

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Jason Lightfoot ♦♦ Jonathan commented · Dec 01, 2020 at 03:41 PM

I meant in a model where we can step through and see if something funky is happening, since the description you gave is perfect and should work as far as I can tell.

You could try stepping through with the debugger and put expressions in the watch list to see what everything is evaluating to.

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Jonathan Jason Lightfoot ♦♦ commented · Dec 01, 2020 at 03:58 PM

I've already implemented and saved over using Math.fmod() and it's working now.

What it seemed to be doing is that the even values never evaluated to a 0 remainder with "% 2".

As far as the debugger I haven't used that yet. I'm not sure how to put in breakpoints and watch specific variables in flexsim.

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