Is there a reason I shouldn't be testing a set of variables for 0 by testing their product?

Question

Is there a reason I shouldn't be testing a set of variables for 0 by testing their product? Often in my coding across different languages I will test a set of variables to do something if they all consist of zeros. For example (c#): ``` if( myString.Length * myInt * (myUrl.LastIndexOf(@"\")+1) == 0 ) ``` Instead of: ``` if( myString.Length == 0 || myInt == 0 || myUrl.LastIndexOf(@"\") < 0) ``` Is there a reason I shouldn't be testing this way?

Accepted Answer

Here are a few reasons. All are important, and they're in no particular order.

- Short circuiting. In your first example, all three things will be evaluated even if they don't need to be. In some cases, this can be a real problem: short circuiting is nice because you can do things like `if (myObj != null && myObj.Enabled)` without throwing exceptions

- Correctness. Is `myString.Length * myInt * myUrl.LastIndexOf(@"\") == 0` actually equivalent in all practical cases to `if( myString.Length > 0 && myInt != 0 && myUrl.LastIndexOf(@"\") <= 0)`? I'm not sure. I doubt it. I'm sure I could figure it out with some effort, but why should I have to in the first place? Which brings me to...

- Clarity. Since the conventional way is to use separate statements and `&&`, anyone reading this code in the future will have a harder time understanding what it's doing. And don't make the excuse that, "I'll be the only one to read it", because in a few months or years, you'll probably have forgotten the thoughts and conventions you had when you wrote it, and be reading it just like anyone else.

Is there a reason I shouldn't be testing a set of variables for 0 by testing their product?

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