Maximum and Minimum monoids

[John Lato]

+1 for something like this.  I've written these at least once, and
encountered them on a few more occasions.

I would prefer specific types as Roman suggests, I think.  I prefer to
match on Plus/MinusInfinity rather than going via Maybe.

John L.


> From: Roman Cheplyaka <roma at ro-che.info>
> Subject: Re: Maximum and Minimum monoids

To: Gabriel Gonzalez <gabriel439 at gmail.com>
> Cc: libraries at haskell.org
> Message-ID: <20121227202510.GA24842 at sniper>
> Content-Type: text/plain; charset=us-ascii
>
> Wouldn't it be better to have a real algebraic type instead of wrapping
> Maybe?
>
> Something like
>
>   data Maximum a = MinusInfinity | Maximum a
>   data Minimum a = PlusInfinity  | Minimum a
>
> Maximum x is more concise than Maximum (Just x), and MinusInfinity is
> more descriptive than Maximum Nothing. getMaximum/getMinimum functions
> can still return Maybes.
>
> Anyway, I'm +1 to having something along these lines.
>
> Roman
>
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