[Haskell-beginners] phantom type

[Francesco Ariis]

On Sat, Mar 31, 2018 at 07:54:50AM +0000, PICCA Frederic-Emmanuel wrote:
> I create a method
> 
> myMethod :: MyData Collect -> IO ()
> 
> but I want my method to work for MyData Collect and Mydata Caracterization but not Unchecked.
> 
> So It seems to me that I can not just do
> 
> myMethod :: MyData t -> IO ()
> 
> 
> what is the right way to solve this problem ?

Hello Frederic,
    I am in a rush so I cant write a minimal example, but wouldn't
a typeclass + make Collect and Cara instances of that typeclass do?
-F