[Haskell-cafe] Is it acceptable if Applicative behave not like a Monad

Kim-Ee Yeoh ky3 at atamo.com
Thu Apr 30 16:07:27 UTC 2015

On Thu, Apr 30, 2015 at 10:49 PM, Adam Bergmark <adam at bergmark.nl> wrote:

> Yes it's okay and sometimes expected for them not not behave the same, but
> see e.g. haxl and ApplicativeDo.

This is a value of okay I've never seen before.

> For example, the applicative version may run foo and bar in parallell. But
> using monad they run sequentially.

What if pure weren't a perfect synonym for return?

What if the methods of the semigroup instance didn't match those of the

The mind boggles at the confusion that would result.

Such cases typically call for newtypes to sort out the effect classes.

-- Kim-Ee
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