Applicative ((,) a)

Conal Elliott conal at
Fri Mar 9 20:23:06 EST 2007

What was the motivation for providing the following Applicative instance?

instance Monoid a => Applicative ((,) a) where
    pure x = (mempty, x)
    (u, f) <*> (v, x) = (u `mappend` v, f x)

Is this instance described in "Applicative Programming with
I didn't spot  a mention.

Thanks,  - Conal
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