applicatives

So if you can write what you want using applicatives rather than monads, you should prefer applicatives, the argument goes.

Mathematically speaking applicatives are less restrictive since more things can be applicatives than monads.

Absence of applicatives or monads mean that you have to explicitly pattern match on Just/Nothing everytime.

> Absence of applicatives or monads mean that you have to explicitly pattern match on Just/Nothing everytime.

Significant use of applicatives in day-to-day code is a relatively new development in the Haskell community.

Maybe this paper[0] on using Applicatives for performance and concurrency in Haskell's Haxl will help.

But I would not go back to a language without Option (and Applicatives etc.) usage in it's culture.

If the applicative code is better, it's because applicatives are strictly less powerful than monads, in the sense that everything you can do with applicatives you can also do with monads, but not vice-versa.

I am guessing there are commonly accepted idioms and libraries around the use of functors, monads, applicatives, etc..

The pictures/diagrams in it helped me really make sense of applicatives, functors, and monads.

The counter-argument, that applicatives are somehow more complicated or less clear than monads, is a poor one, I think.

Want to know more about Functors and Monads (maybe even applicatives O_o)?

If you are interested in more information about functor, applicative, and monad check out Adits awesome "Functors, applicatives, and monads in pictures" tutorial[1].

It turns out that you have to "know what branch to go down before you start" in exactly the kind of way applicatives allow and monad preclude.

("sensibly" here means that there are type class laws which have to hold) Every Monad is also an Applicative functor, since you could use do notation to compose your promises instead, but there are other interesting Applicatives which do not come from Monads.

When we're dealing with such concerns every day ("I'd like to allow X, but don't want anyone to abuse it and end up with Y") then monads (and functors and applicatives, which they're based on) are really useful as standard APIs for allowing arbitrary operations to be performed, under the control of the API.

Hopefully we can deprecate it in favor of pure now that all Monads must be Applicatives.

Applicatives are definitely something that every Haskell programmer knows.

Check out Functors, Applicatives, And Monads In Pictures[3].