Infinity (CASC.md §6.3): inf, +inf or -inf. The BEAM's floats have no infinity, so CASC's is a value of its own.

Not the atoms :infinity and :neg_infinity, which it once was: those are atoms a document can write -- infinity is not a reserved word -- and then the atom and the number read back as the same thing.

iex> {:ok, %{"x" => x}} = Cooper.load_string("#@version = 1.0\nx = -inf", dotenv: false)
iex> x
%Cooper.Infinity{sign: :negative}