TExp Num?

texp-num.hs

instance Num a => Num (Q (TExp (SomeNamedWith IsNonzero a))) where
  fromInteger 0 = error "It's zero, fool!"
  fromInteger n = [|| someNamedWith IsNonzero (fromInteger n) ||]

fine :: Double
fine =
  case $$(1) :: SomeNamedWith IsNonzero Double of
    (SomeNamedWith p divisor) ->
      divide p 123 divisor
      
  --- or

newtype NonZero = NonZero Integer
 deriving (Show)

instance Num (Q (TExp NonZero)) where
  qa + qb = error "Nope."
  qa * qb = error "Nope."
  abs x = [|| let NonZero y = $$x in NonZero (abs y) ||]
  signum x = [|| let NonZero y = $$x in NonZero (signum y) ||]
  negate x = [|| let NonZero y = $$x in NonZero (negate y) ||]
  fromInteger x = if x /= 0 then [|| NonZero x ||] else error "Zero!"