Functor => Pointed => Applicative => Monad
wren ng thornton
wren at freegeek.org
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.
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