Type extensions

[Ronald Legere]

Greetings.
  I have decided to try and understand the type
system of haskell with extensions. As far as I
can tell, the following set of extensions has
been included, for example in ghc:
   multiparameter type classes
   constructor classes
   existential types
   explicit universal quantification
   scoped type signatures
   funtional dep?? Etc
   

 

There is probably some overlap, and
probably missed a few, as i do not understand
what all these things do! ! 
My question:
  How do you get started learning all this? which of
these is the most important? Is there
a paper out there that explains most or all of these
extensions and why you would want them and HOW the
heck they work together?

Ron Legere

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