[rpglover64]

> it's just a formula. I also know it doesn't do any logging, or "launch nukes", and that it is thread safe.

So the type claims. Without looking at the implementation or using `-XSafeHaskell`, you don't know if there's an `unsafePerformIO` call lurking.

/pedantry

[Buttons840]

Even if the function had documentation that said "this function does not have side effects" it could still have side effects.

So within the context of this thread, type signatures vs hand written documentation, I would say your point is a +0 for hand written documentation. Both type signatures and hand written documentation can lie.