alt Hacker NewsFrom the tutorial:
// Division by zero is not an error
io.debug(3.14 /. 0.0)
It prints 0
Yuck. Division by zero is an unfortunate reality but basically nobody with mathematical background thinks that just defining x/0 = 0 is a good solution.
Often in numerical computing, getting an NaN or Inf is a blessing in that it’s a hint that your algorithm is numerically buggy, in the same way that a crash or a exception would indicate a program bug.
This approach is the numeric equivalent of a program continuing on after an undefined variable, just assuming it’s 0. That was tried by scripting languages in the 90s and these days most folks think it was a bad approach.
Replies
I wouldn't call myself a person with a mathematical background, but there are those people who believe it's just fine. [0] I don't have enough knowledge to debate that, but it would seem to disprove "basically nobody". Zero is a convention, like NaN or Inf are conventions.
A problem that Gleam has here is that the Erlang runtime does not have NaN or Inf in its float type (or integer type for that matter). It could be represented with an atom, but that would require an atom and a float having the same type in Gleam, which is not something the type system can do (by design). The operator could, in theory, return a Result(Float, DivisionByZeroError), but that would make using it very inconvenient. Thus zero was chosen, and there is an equivalent function in the stdlib that returns a result instead, if you wish to check for division by zero.
I have no math background but every line of code I wrote that involved a division, I just wished that division by 0 results in 0, so this actually resonated with me
Regardless of what happens in the language, this needs to be handled.
In python for instance, the developer needs to be prepared to catch a divide by zero exception.
In gleam, the same consideration is required but the implementation will just differ.
I don't actually see an issue here. It's a potential gotcha, but once you are aware of this feature of the language, it's no different than any other.
Defining x/0 as 0 doesn’t break anything mathematically; all the relevant field axioms have an x != 0 hypothesis so this really is undefined behavior.
Moreover, it’s actually pretty common for proof assistants to adopt the x/0 = 0 convention, as it turns a partial function into a total one! Having something like NaN or Inf is definitely a better solution in practice, but x/0 = 0 does have its merits!
Yeah you can really get yourself into trouble if you make dividing by zero zero. It's a strong indication that you have done something horribly wrong in your code upstream of that point. Why would you throw away that signal?
INTERCAL. It just skips lines if they're syntactically invalid or cause a runtime error; it just skips them and keeps going.
The divide-by-zero thing is explained here[1]. The relevant bits:
> Gleam does not implicitly throw exceptions, so throwing an exception is not an option. The BEAM VM does not have a Infinity value, so that is not an option. Therefore Gleam returns 0 when dividing by zero.
> The standard library provides functions which return a Result type for division by zero which you can use if that is more suitable for your program.
You can also use Guards[2] to prevent handle a divide-by-zero situation before you attempt it.
[1] https://gleam.run/frequently-asked-questions/#why-does-divis...
[2] https://tour.gleam.run/everything/#flow-control-guards