Re:Swift Functors, Applicatives, and Monads in Pictures
by dllthomas on Wednesday July 15, 2015 @12:09PM
(#9892101)
One thing that I really like about Haskell's practice of naming interfaces after mathematical constructs is that it makes it clear what the rules for those interfaces "should be" and changes the character of a few kinds of discussion.
If we called them "Mappable", "Applicable", "FlatMappable" (yuck), "AssociativeAppendableWithIdentity"... then there would be disagreement about whether some new construct "is really" Applicable. Is summation really "Appending"?
And these arguments are high stakes, because the most important thing about an interface is that it tells the user what they can expect. If I ask for an Appendable, and get something that doesn't follow the rules I think Appendable should have, then... whose code is broken?
In Haskell, it's entirely clear whether a new type "is really" a Monoid or Functor - does it obey the laws? Okay!
Whether "container" is a good way to think of Functor is recognized as a purely pedagogic question (not that there's never drama in pedagogy, but those people getting work done can opt out without worry that it will break their code when they try to interface with others).
If we called them "Mappable", "Applicable", "FlatMappable" (yuck), "AssociativeAppendableWithIdentity"... then there would be disagreement about whether some new construct "is really" Applicable. Is summation really "Appending"?
And these arguments are high stakes, because the most important thing about an interface is that it tells the user what they can expect. If I ask for an Appendable, and get something that doesn't follow the rules I think Appendable should have, then... whose code is broken?
In Haskell, it's entirely clear whether a new type "is really" a Monoid or Functor - does it obey the laws? Okay!
Whether "container" is a good way to think of Functor is recognized as a purely pedagogic question (not that there's never drama in pedagogy, but those people getting work done can opt out without worry that it will break their code when they try to interface with others).