[Haskell-cafe] least fixed points above something

[Edsko de Vries]

I've used a similar function myself, but why write it in such a  
complicated way? How about

lfp :: Eq a => (a -> a) -> a -> a
lfp f x
   | f x == x = x
   | otherwise = lfp f (f x)

Edsko

On 19 Mar 2009, at 09:49, Jens Blanck wrote:

> Hi,
>
> I found myself writing the following
>
> leastFixedPoint :: (Eq a) => (a -> a) -> a -> a
> leastFixedPoint f x = fst . head . dropWhile (uncurry (/=)) $ zip l  
> (tail l)
>     where l = iterate f x
>
> and was a bit surprised that I couldn't get any matches on hoogle  
> for the type above. The closest one is fix :: (a -> a) -> a but that  
> sort of assumes that we're starting the fixed point search from the  
> bottom element (undefined).
>
> Anyway, is there a nicer way of doing the above?
>
> Jens
>
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe