But of course, the function in question isn’t Math.Round. It’s “interpretDotNetFunction”. Which is, necessarily, “string -> IO ()” (forgive my syntax).

You could make it compile in Haskell. You just shouldn't:

f x = unsafePerformIO $ print "boom" >> return (pi * x)

In what language?

Haskell

You can't console.log either...

There is Debug.Trace.trace which does the trick with unsafePerformIO (which is a special non-type-safe escape hatch for IO)