[Haskell-cafe] type Rational and the % operator
ryani.spam at gmail.com
Sat Mar 28 23:17:53 EDT 2009
Just use "/" for division. % is for construction of rationals from
the "underlying" numeric type.
For example, instead of "toRational x" you can write "x % 1".
2009/3/28 michael rice <nowgate at yahoo.com>:
> I may be missing something here, but this is what I intended.
> An expression of the form
> a1 + ------
> a2 + ------
> a3 + --
> a4 + ...
> Where the ai's are positive integers is called
> a continued fraction.
> Function cf should take [1,2,6,5] to produce
> 1 + -----
> 2 + -----
> 6 + --
> --- On Sat, 3/28/09, Brandon S. Allbery KF8NH <allbery at ece.cmu.edu> wrote:
> From: Brandon S. Allbery KF8NH <allbery at ece.cmu.edu>
> Subject: Re: [Haskell-cafe] type Rational and the % operator
> To: "michael rice" <nowgate at yahoo.com>
> Cc: "Brandon S. Allbery KF8NH" <allbery at ece.cmu.edu>, "Duane Johnson"
> <duane.johnson at gmail.com>, haskell-cafe at haskell.org
> Date: Saturday, March 28, 2009, 10:39 PM
> On 2009 Mar 28, at 22:36, michael rice wrote:
> import Data.Ratio
> cf :: [Integer] -> Rational
> cf (x:xs) = (toRational x) + (1 % (cf xs))
> cf (x:) = toRational x
> cf  = toRational 0
> Data.Ratio> :load cf.hs
> ERROR "cf.hs":3 - Type error in application
> *** Expression : toRational x + 1 % cf xs
> *** Term : toRational x
> *** Type : Ratio Integer
> *** Does not match : Ratio (Ratio Integer)
> Your function cf produces a Rational (Ratio Int); you're using it in the
> denominator of another Ratio, which makes that Ratio's type Ratio (Ratio
> Int). This is almost certainly not what you intended, but I couldn't say
> what you actually want.
> brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
> system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
> electrical and computer engineering, carnegie mellon university KF8NH
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