The problem is that is more than one way to compose two applicative functors! If one is a pointed functor and the other is a monad, then there are at least 3 different forms of distributive laws that might be used to compose them to obtain a monad (and as a side effect, obtain an applicative) in addition to the closure of applicative functors under composition. <div>
<br></div><div>I would strongly advise against enshrining applicative/applicative composition directly in Control.Applicative. If you want to place it in something off to the side like Control.Applicative.Composition, then by all means.<div>
<br></div><div>-Edward Kmett.<br><br><div class="gmail_quote">On Wed, Jun 17, 2009 at 5:33 PM, Henning Thielemann <span dir="ltr">&lt;<a href="mailto:lemming@henning-thielemann.de">lemming@henning-thielemann.de</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><br>
In the TypeCompose package there is the O data type for composing two applicative functors<br>
   <a href="http://hackage.haskell.org/packages/archive/TypeCompose/0.6.4/doc/html/Control-Compose.html" target="_blank">http://hackage.haskell.org/packages/archive/TypeCompose/0.6.4/doc/html/Control-Compose.html</a><br>

<br>
However I hesitate to import this package because of a lot of needed type extensions. But since &#39;O&#39; seems to be the canonical way for combining two functors, could we add it to Control.Applicative?<br>
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</blockquote></div><br></div></div>