Re: [Haskell-cafe] Questions about the Functor class and it's use in "Data types à la carte"

Yitzchak Gale gale at
Sat Dec 15 22:43:05 EST 2007

> Ah, good old seq. How I loathe it.
> Seriously, though, good catch. I always forget about seq when I'm doing
> stuff like this.

When using seq and _|_ in the context of categories,
keep in mind that Haskell "composition" (.)
is not really composition in the category-theoretic
sense, because it adds extra laziness. Use this

(.!) f g x = f `seq` g `seq` f (g x)


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