Works like a charm. Here's a final copy for those interested. Michael ===== import Data.Ratio cf2 :: Rational -> [Int] cf2 a = let ai = floor a             air = toRational ai         in ai : if a == air then [] else cf2 (1 / (a - air)) --- On Sun, 3/29/09, Miguel Mitrofanov wrote: From: Miguel Mitrofanov Subject: Re: [Haskell-cafe] Rational and % operator remix To: "michael rice" Cc: "Lennart Augustsson" , haskell-cafe@haskell.org Date: Sunday, March 29, 2009, 4:25 PM cf2 a = let ai = floor a             air = toRational ai         in ai : if a == air then [] else cf2 (1 / (a - air)) On 30 Mar 2009, at 00:19, michael rice wrote:

I'm a Lisper, kind of feeling my way around here in Haskell, so please bear with me.

I did the things you suggested, but I think the last one may have gotten garbled. Anyway, this is what I ended up with

cf2 :: Rational -> [Int] cf2 a = let ai = floor a              in                if a == (toRational ai)                  then [ai]                  else ai : cf2 (1 / (a - ai))

but I'm still at least one error short of a clean run

Main> :load cf.hs ERROR "cf.hs":7 - Type error in application *** Expression     : ai : cf2 (1 / (a - ai)) *** Term           : ai *** Type           : Ratio Integer *** Does not match : Int

Where did I go wrong or what did I leave out?

Michael

--- On Sun, 3/29/09, Lennart Augustsson wrote:

From: Lennart Augustsson Subject: Re: [Haskell-cafe] Rational and % operator remix To: "michael rice" Cc: haskell-cafe@haskell.org Date: Sunday, March 29, 2009, 2:29 PM

You can use floor in a Rational directly, no need to take it apart and divide.

There is no need to write (toRational 1), just write 1.

Don't write (subtract ai a), write (ai - i).

You also have a type error; the ai should no be a Rational, so you need to move to toRational call to the comparison.

   -- Lennart

2009/3/29 michael rice :

...

Hi,

Thanks again for the help last night.

The second function cf2 is an attempt to reverse the process of the first function, i.e., given a rational number it returns a list of integers, possibly infinite, but you shouldn't get into trouble if you use 98%67 as input (output should be [1,2,6,5]). The interpreter is complaining about the '=' following the 'in' keyword. Is there a better way to state this?

Michael

import Data.Ratio cf :: [Int] -> Rational cf (x:[]) = toRational x cf (x:xs) = toRational x + 1 / cf xs

cf2 :: Rational -> [Int] cf2 a = let ai = toRational (floor ((numerator a) / (denominator a)))              in                if a = ai                  then [a]                  else ai : cf2 ((toRational 1) / (subtract ai a))

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