On Thu, Jul 14, 2005 at 01:44:05PM +0300, Yitzchak Gale wrote:
> Here it is translated into regular monad syntax:
>
> > coinsM _ 0 k = return []
> > coinsM _ _ 0 = []
> > coinsM cs a k = do
> > t <- init (tails cs)
> > let h = head t
> > unless (h <= a) []
> > s <- coinsM t (a-h) (k-1)
> > return (h:s)
>
> (The function "unless" is from the Control.Monad
> module.)
[] is an instance of MonadPlus, which allows you to use "guard" instead
of "unless ...":
guard (h <= a)
Best regards
Tomasz
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