Pretty printing

[LSLeary]

I need to present polynomials to users with particular variable names in as clean a form as possible, as such, I've written and am using ppPoly:

ppPoly :: UPoly Double -> Text -> Text
ppPoly p var = fold $ go (U.length coeffs - 1)
 where
  coeffs = unPoly p
  go -1 = []
  go  n = ppSign n (signum coeff)
       <> ppDouble 'g' 1 (abs coeff)
       <> ppPower (" " <> var) n
        : go (n - 1)
   where
    coeff = coeffs U.! n
    ppSign m x
      | m == U.length coeffs - 1 = if x < 0 then  "-"  else ""
      | otherwise                = if x < 0 then " - " else " + "
    ppPower _    0 = ""
    ppPower base 1 = base
    ppPower base k = base <> "^" <> pack (show k)

ppDouble :: Char -> Int -> Double -> Text
ppDouble c n x = pack (printf ("%.*" ++ [c]) n x)

It's one of the building blocks I intend to expose, but ideally pretty printing would move into (and be provided by) poly instead.
I don't have any intention to make a PR at this point in time, but anyone who wants to do so is free to adapt the above.

[Bodigrim]

It's difficult to provide an efficient one-size-fits-all for prettyprinting, so it would require design work from a potential future contributor.