Why should I use asserts?

Question

I never got the idea of asserts -- why should you ever use them?

I mean, let\'s say I were a formula driver and all the asserts were things like security belt, helm

Answer 1

I NEVER use assertion in my code, I hate them with passion. I understand the need for error checking and handling but to prevent an error that would crash your program by crashing your program yourself .... frankly I do not see the advantage.

Also leave one assertion in your code and murphy's law will ensure that it will, eventually, crash your program. I much prefer checking the data before I do processing with it and throw the appropriate exception so it is handled much like any other exceptional states or operation. This in my experience yielded software that was much more stable in the long run with deterministic behavior from the user's stand point.

You as a software engineer will know what to do when your program asserts out, most users will just get scared they broke something and will end up not using your software. So unless you are developing for engineers (which is quite possible) and even then...

From a usability stand point asserts are horrible, even if they are not "supposed" to happen we all know that eventually it will...

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Ok... From all the comment and fire I am getting here I think I need to further explain my point of view because it is clearly not understood.

I did not say I was not checking for exceptions, weird values or just plain wrong states, I just said I did not use assertions because of the horrible way they tent to close the system from a end-user's perspective. Also most modern languages provide another, type-safe way to handle these situations, whey then would I use assert when a perfectly good exception would do the trick, and quite nicely so too.

In most production code I have seen out there I noticed mainly two ways to deal with this, buttering asserts all over the code and then leave a good bunch in production. This has the infuriating tendency to just close the application to the user, I have yet to see an Assert gracefully fail a system.... it just fails it ... boom... gone... end user just saying "WTF is a assertion failed error at address 0x330291ff!!!"

The other way, even worst if you ask me, was to just catch whatever was thrown and hide it under the carpet (ever seen these dreadful try-catch with empty braces !!)

NEITHER WAY will work to get a good stable system. Sure you can use asserts in your beta code and remove them all in your production code... but why the hell would you remove your safety nets because it is production. I would be very surprised that all these checks would cripple your system's performances.

Build yourself a good exception handling scheme and .. by god... LEAVE IT THERE, you will get much more meaningful information our of your system and if done appropriately always in context than having some deep library throwing asserts because something is missing.

This is especially true when creating libraries... to think you, the creator of the library, can decide when to bring down the whole system because something went wrong in the data that was thrown at you is incredibly selfish and narrow minded. Let the user of your library decide what is sufficiently important that it should warrant emergency failure.

so no... I do not use asserts... I use exceptions

And yes... usually the code that fails in production has rarely my name on top.