Functor => Pointed => Applicative => Monad

wren ng thornton wren at
Tue Nov 30 06:32:18 CET 2010

On 11/29/10 2:08 PM, Tyson Whitehead wrote:
> As to whether it should go (Pointed, Functor) =>  Applicative or Pointed =>
> Functor =>  Applicative, it would seem to me that,

Not all functors are pointed therefore Pointed=>Functor is invalid. 
Leaving them unordered or requiring Functor=>Pointed are the only options.

Essentially, for T :: * -> *, pointedness is saying that there is a 
trivial embedding of the parameter, a, into T a; whereas functoriality 
is saying that T is structural over its parameter. Surely the latter is 
"more complicated", but they're rather different concepts.

Live well,

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