Why is "NaN" a possible value for type "Int" in Elm?

Question

Recently, I began to study Elm. When I saw the type Int, I assumed that it was something like Haskell Int, which (I think) is an integer.

But I was surprised to see this:

> Result.withDefault 0 <| String.toInt "-"
NaN : Int

NaN- A floating-point concept that does not seem to apply to integers. It looks like it could be a leak from JS, which implies that it Intappears to be JS Number.

This is true? Why was this design decision made, and where can I find out about it?

(In addition, two minor questions:

• Why not a NaNvalid literal?
• How to check that the value is Intnot NaN? The function isNaNis of type Float -> Bool http://package.elm-lang.org/packages/elm-lang/core/latest/Basics#isNaN

)

Answer 1

NaNis not a valid value Int. This is a bug in a package elm-lang/corethat has been fixed on the main but not yet released.