[Haskell-cafe] Rational and % operator remix
miguelimo38 at yandex.ru
Sun Mar 29 16:25:09 EDT 2009
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
> 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?
> --- On Sun, 3/29/09, Lennart Augustsson <lennart at augustsson.net>
> From: Lennart Augustsson <lennart at augustsson.net>
> Subject: Re: [Haskell-cafe] Rational and % operator remix
> To: "michael rice" <nowgate at yahoo.com>
> Cc: haskell-cafe at 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 <nowgate at yahoo.com>:
> > 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
> > 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
> > in
> > if a = ai
> > then [a]
> > else ai : cf2 ((toRational 1) / (subtract ai a))
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