# Tutorial photo gallery **URL:** \ **Category:** Uncategorized\ **Created:** [March 2, 2003, 12:45am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726 "2003-03-02T00:45:06Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![chapster](https://avatars.discourse-cdn.com/v4/letter/c/958977/32.png) [@chapster](https://forum.kirupa.com/u/chapster)\ **Post date:** [March 2, 2003, 12:45am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/1 "2003-03-02T00:45:06Z")
Ok I have read through the tutorial on [[COLOR=red]Photo Gallery [/COLOR] ](http://www.kirupa.com/developer/mx/photogallery.htm) and this is the only part I do not understand ```auto this.pIndex = (this.pIndex+d)%this.pArray.length; if (this.pIndex<0) { this.pIndex += this.pArray.length; } ``` I never got how to work that modulo division operator. That whole section I am confused. I guess because I can’t vision how it works. Can someone explain this is detail and simple for stupid people like me. Thanks in advance ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 12:50am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/2 "2003-03-02T00:50:08Z")
This thread should explain the modulo operator… [http://www.kirupaforum.com/showthread.php?s=&threadid=7095](http://www.kirupaforum.com/showthread.php?s=&threadid=7095) ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 1:43am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/3 "2003-03-02T01:43:07Z")
Hey thanks for that link but there is still something I am not getting. I did a little test. ```auto function temp() { trace("MODUL0 : " +(a++)%20); trace("A : "+a); } ``` so every time you click a button it trace this function. lets say: a=4 % 20 this would be 5 now the modulo operator takes the remainder of the result in this case there is no remainder. so how come when a=5 the trace for the modulo = 4 I can see it working in the trace where a=1 trace=0 a=2 trace=1 a=3 trace=2 and so on What am I not getting here. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 4:18am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/4 "2003-03-02T04:18:42Z")
4%20 is the remainder of 4 divided by 20. What you want is the remainder of twenty divided by 4 (20%4). Which in actuality does return 0 😉 ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 6:47pm UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/5 "2003-03-02T18:47:58Z")
Ok so that will return 4 so then 5%20 will return 4 as well but this shows in the trace as 5 I’m still not getting it. Forgive me for be stupid but can you show how it reaches twenty through its math. ok lets make it easier say reaches 7. Thanks for your patience with this question ```auto function temp() { trace("MODUL0 : " +(a++)%7); trace("A : "+a); } ``` ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 6:54pm UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/6 "2003-03-02T18:54:58Z")
You are still having it reversed. In essense you are getting the remainder of a/7, but from what you are saying you want the remainder of 7/a. Try this… ```php function temp() { a++; trace("A : "+a); trace("MODUL0 : "+7%a); } ``` This is what I get in the output for that… > A : 1 > MODUL0 : 0 > A : 2 > MODUL0 : 1 > A : 3 > MODUL0 : 1 > A : 4 > MODUL0 : 3 > A : 5 > MODUL0 : 2 > A : 6 > MODUL0 : 1 > A : 7 > MODUL0 : 0 Which is all correct. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 7:18pm UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/7 "2003-03-02T19:18:01Z")
Ok I see that but here is what I get when I turn it the other way the way the % modulo works. ```auto function temp() { a++; trace("A : "+a); trace("MODUL0 : "+a%7); } ``` ```auto A : 1 MODUL0 : 1 A : 2 MODUL0 : 2 A : 3 MODUL0 : 3 A : 4 MODUL0 : 4 A : 5 MODUL0 : 5 A : 6 MODUL0 : 6 A : 7 MODUL0 : 0 ``` Ok I take a calcalator and devide 7 into a 1%7=7 2%7=3.5 3%7=2.3333333 4%7=1.75 5%7=1.4 6%7=1.1666666 7%7=1 8%7=0.875 Now what I am not getting is how flash is working out its numbers. Ok I am starting to feel really stupid now I hope this will benfit someone else so I don’t feel so alone. Thanks for your help on this ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 7:24pm UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/8 "2003-03-02T19:24:03Z")
I don’t think it works because technically its not a valid equation. num1 % num2 You use modulo to get the remainder of how many times num2 can go into num1. If num2 is bigger than num1, then it is not really valid because the number bigger and cannot go into num1 correctly. So I think Flash gets confused here or something. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 2, 2003, 8:00pm UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/9 "2003-03-02T20:00:16Z")
Ok now I see it clearer when num1 gets up to larger number than num2. example 10%7 the remainder would be 3 this now makes sence Thank you for your patience. How else would you use this operator. or what other purpose could you use it for. I don’t have any other example than the one I have done here but in the world of flash how else can it help one. And thanks again for your patience with this question. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 3, 2003, 2:56am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/10 "2003-03-03T02:56:22Z")
You know what… I actually very rarely use Modulo :-\ Whatever case you can think of that might involve you needing to know the remainder of two numbers you can use modulo for 😛 I don’t know exact situations. Sorry. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [March 3, 2003, 2:58am UTC](https://forum.kirupa.com/t/tutorial-photo-gallery/14726/11 "2003-03-03T02:58:44Z")
Not to worry maybe someone else can answer this question. You have been so helpful and patient. Thanks again. 🙂