[Haskell-beginners] implicit or shorthand class instances?

Alexander Bernauer alex-haskell at copton.net
Fri Nov 30 14:42:43 CET 2012

On Thu, Nov 29, 2012 at 12:52:38PM -0900, Christopher Howard wrote:
> Is there any special extension or syntax trick that would allow me to
> reduce the amount of this repetitious code?

I am not aware of any (which doesn't mean there is none).

I would hack a few lines of Template Haskell for this. Should be pretty
straight forward.

Use the thee quotation operator like so
[| {- code -} |] 
to get the Haskell AST of this code snippet and pretty print it. Then
you have a good starting point for what your TH function should return.

Note, that if the TH function returns 'Q [Dec]' you don't need a splice
operator for top-level declarations. Instead, you can simply write 
data SomeThing = ....

instantiate 'SomeThing
where instantiate is your TH function.

Pretty handy, IMHO.

See [1] for a starting point.



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