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pixie_

Random question - but what happens when you divide by zero in go?

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http://play.golang.org/p/TjzkjvDfYa

For people not familiar with Go Playground, that’s a compiler error.

And here's what it looks like at runtime: http://play.golang.org/p/bVh52aKvMi

Does it only throw a compiler error if you use 0 as a constant? Let's say you have a function that returns an int; does it force you to check if that int is non-zero before using it in division?

It can only throw a compiler error if you use a 0 literal (or constant), because it cannot determine the runtime value of a variable denominator at compile-time (obviously).

It does not force you to check, but if you wanted to "catch" the "exception" (really, "recover from the panic"), here's how you would do that. Note that this is admittedly a somewhat unidiomatic use of recover(): http://play.golang.org/p/dAQ01dus9Y

Which applies not just to integer math, but also to floating point:

http://play.golang.org/p/vEmiqUyPag

Division by zero in floating point is well defined and useful, and does not produce a runtime exception. So why is this a compile time error?

Edit And it produces the wrong result for division by negative zero: http://play.golang.org/p/DKoVG0Vlaf It should be -Inf, not +Inf. Go's floating point math is whack.

Is there any way to 'catch' a divide by zero panic in go?

Sure, http://play.golang.org/p/dAQ01dus9Y

For others: note that that's only because Queue29 assigned 0 to a variable before using it as the denominator, so there's no way for Go to catch that at compile-time.

If you divide by a literal 0, this is a compile-time error, so there's no panic (and no need to recover()): http://play.golang.org/p/E0jSDAHwtg

Interesting thanks. Of course then I was wondering what this recover() stuff was and I found an explanation here - http://blog.golang.org/defer-panic-and-recover cool stuff.

Assuming it's not a division by constant zero that's caught at compile time, it panics. Go's panic/recover system seems conceptually similar to try/catch and exceptions, but they aren't a drop-in replacement for exceptions due to some differences in both style and execution. There's a good blog post[1] on the Go blog going into more detail about defer/panic/recover, if you're interested.

[1]: http://blog.golang.org/defer-panic-and-recover

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