topic Can someone explain Math.fmod() vs using a % operator? in FlexSim Forum

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

jonathan_s3 — Tue, 01 Dec 2020 15:19:12 GMT

[ FlexSim 20.2.3 ]

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().

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

jason_lightfoot_adsk — Tue, 01 Dec 2020 15:28:43 GMT

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?

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

jonathan_s3 — Tue, 01 Dec 2020 15:32:47 GMT

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++;

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

jason_lightfoot_adsk — Tue, 01 Dec 2020 15:41:28 GMT

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.

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

jonathan_s3 — Tue, 01 Dec 2020 15:58:21 GMT

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.

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

jason_lightfoot_adsk — Tue, 01 Dec 2020 16:04:04 GMT

Understood. I really recommend the debugger - it takes out the mystery of many situatons and is pretty simple to use. If you want help on that there's the documentation here or you can reach out for support.

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

jonathan_s3 — Tue, 01 Dec 2020 16:18:17 GMT

While I'm thinking about it, can you step me through the logic of:

current.outObjects[(current.labels.assert("roundRobinVal", 1).value++ - 1) % current.outObjects.length + 1];

as in does it evaluate the .value++ and -1 before or after the %.

The way it reads left to right it would read the roundRobinVal (asserting it to 1 if it did not exist already), then increment it by 1, then -1, then divide it by "current.outObjects.length + 1" to get the final value. But that would mean the .value++ -1 would be self defeating so that's no right. I assume the ++ is done after it evaluates the %.

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

jason_lightfoot_adsk — Tue, 01 Dec 2020 17:16:03 GMT

It's incremented after the expression is evaluated. There's no preincrement yet in flexscript afaik.

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

Matthew_Gillespie — Tue, 01 Dec 2020 17:38:44 GMT

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

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

jonathan_s3 — Tue, 01 Dec 2020 17:42:19 GMT

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