Provides a wide array of semigroupoids and operations for working with
semigroupds.
A semigroupoid is a category without the requirement of identity
arrows for every object in the category.
When working with comonads you often have the <*> portion of an
Applicative, but not the pure. This was captured in Uustalu and Vene's
"Essence of Dataflow Programming" in the form of the ComonadZip class
in the days before Applicative. Apply provides a weaker invariant, but
for the comonads used for data flow programming (found in the streams
package), this invariant is preserved. Applicative function
composition forms a semigroupoid.
Similarly many structures are nearly a comonad, but not quite, for
instance lists provide a reasonable extend operation in the form of
tails, but do not always contain a value.
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