[Haskell-cafe] Control.Alternative --- some and many?

Christopher Done chrisdone at googlemail.com
Wed Jun 23 01:54:45 EDT 2010

I'm not sure how Alternative differs from MonadPlus, other than being
defined for Applicative rather than Monad.  They have the same laws
(identity and associativity).

"Some" and "many" are probably motivated by their usefulness in
parsers.  Hence "optional", etc.  I'm sure there are plenty of other
uses for it.

On 23 June 2010 05:22, Gregory Crosswhite <gcross at phys.washington.edu> wrote:
> Hey everyone,
> Could someone explain to me (or point me to a reference explaining) the
> purpose of the "some" and "many" methods of the Alternative class?
> Also, there is a link posted in the documentation for Control.Applicative to
> a paper which describes the motivation behind the Applicative class;  is
> there similarly a paper explaining the motivation behind the Alternative
> class?  (The problem with Googling for "Alternative" is that this word is
> used a whole lot of the time, and very rarely does it refer to the
> Alernative class.  :-) )
> Cheers,
> Greg
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