Why does this not trigger a warning, when it works...

# getting-started

[ascii]

Why does this not trigger a warning, when it works for Ints?

val zero = if (condition) 0f else 0f
val division = 1f / zero // no division by zero warning

[ascii]

Of course proper test coverage would catch this easily, but given that tests are written by humans, sometimes it slips through.

[ephemient]

division by floating point zero is not an error

[ascii]

Oh yes, infinity. But then there's this inconsistency:

[ephemient]

ah, I guess that's an IDE limitation. it doesn't seem to warn about

val zero = if (condition) 0 else 0
val division = 1 / zero

either

[Robert Williams]

Surprised there isn't a specific warning for if (x) y else y

[Robert Williams]

I suppose it'd be difficult to detect in anything other than the most simple cases but that's also true of division by zero 🤷

[Robert Williams]

Actually, ignore that, kotlin compiler doesn't try to make any guarantees about runtime correctness (that's why we have tools like detekt)

[Robert Williams]

You only get the divide by zero warning when it tries to do the division at compile time

[Robert Williams]

Which in this case looks like an implementation detail of the compiler:

We use the term “constant expression” to refer to any expression constructed of the following:

constant literals

access expressions to enum entries

string interpolation over constant expressions

an implementation-defined set of functions that can always be evaluated at compile-time

[Robert Williams]

Fun fact: Java does actually guarantee that this will happen at compile time if the condition is a constant

[Robert Williams]

So the Java equivalent will give the expected warning on both lines:

``` int x = true ? 0 : 0;

int y = 1 / x;```