Comments on: generating a unique range of numbers

By: Interesting Finds: 2009 02.23~02.27 - gOODiDEA.NET

Interesting Finds: 2009 02.23~02.27 - gOODiDEA.NET — Fri, 27 Feb 2009 02:27:31 +0000

[...] Generating a unique range of numbers Published Thursday, February 26, 2009 9:26 PM by gOODiDEA Filed under: Interesting Finds, .NET, Javascript, MSMQ, Prototype, jQuery, WinDbg, IIS [...]

By: Gregg

Gregg — Thu, 26 Feb 2009 20:02:07 +0000

Hi Stephen,

Yes you are right. I have probably never seen a problem with this when using it because it’s normally executing in a controlled loop where I know exactly how many times I’m calling it and so size_ never gets to 0. I’ll update the code to just do a ‘<=’ in the GetRandomNumber as I think that will do what I expect it to.

I think with set of size 0 thing it could either do as you suggested, or just throw an exception to say 0 is an invalid argument. I will leave this out the code though to make it a little easier to read in the article.

Thanks for the comment though, great spot.

Gregg

By: Stephen Parker

Stephen Parker — Thu, 26 Feb 2009 19:30:35 +0000

I think you’re off-by-one in your range check in GetRandomNumber. It will allow size_==0 into Delete and allow you to access the -1′th element of the array. (Alternatively you could consider that if you ask for a set of size 0 then the first random number request will be accepted as being zero or greater.)