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<@U4UGS5FC7> <@UM95PD31P> why do we have type `Nothing` in this: `fun &lt;A&gt; absurd(): (Nothing) -&gt; A`, but not `Unit`?
<https://github.com/arrow-kt/Category-Theory-for-Programmers.kt/blob/master/src/main/ank/1.5-products-and-coproducts.md>

Like it is written in CTfP book: "In the category of sets and functions, the initial object is the empty
set. Remember, an empty set corresponds to the Haskell type Void (there
is no corresponding type in C++) and the unique polymorphic function
from Void to any other type is called absurd"

So `Nothing` in Kotlin is the initial type for everything else?

It's called `absurd` because you can never call it. And you can not call it because there are no instances of type Nothing. We do have a single Unit instance in Kotlin

absurd / undefined closest is TODO() in Kotlin

Nothing is bottom of all types and also a subtype of all types as Stojan said with no inhabitants. The only way to write a non suspend function that returns Nothing is throwing an exception since we can't construct or obtain a value of Nothing.

Suspended functions can exit with Nothing without throwing though by shifting in their scope