[Haskell-cafe] distinguish functions from non-functions in a class/instances

[Philipp N.]

oleg-7 wrote:
> 
> 
> In fact, that distinction is possible. The following article
> 
> 	How to write an instance for not-a-function
> 	http://okmij.org/ftp/Haskell/typecast.html#is-function-type
> 
> specifically describes a method of writing an instance which is
> selected only when the type in question is NOT a function. The method
> is quite general and has been extensively used (for example, to
> implement deep monadic join).
> 
> 

That's really incredible, and yet I don't quite understand how IsFunction
works.
Here is my very short but powerful solution (nary is renamed to wrap).
http://www.nabble.com/file/p14220591/wrap.hs wrap.hs 

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