[Haskell-cafe] Pointless functors

[Eugene Kirpichov]

'An arbitrary element' means 'undefined will suffice'

point x = fmap (const x) undefined


2009/3/13 Ross Paterson <ross at soi.city.ac.uk>:
> On Fri, Mar 13, 2009 at 03:18:15PM +0100, Martijn van Steenbergen wrote:
>> Are there any functors f for which no point/pure/return :: a -> f a exists?
>
> No.  Choose an arbitrary element shape :: f () and define
>
>        point x = fmap (const x) shape
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-- 
Eugene Kirpichov
Web IR developer, market.yandex.ru