[Haskell-cafe] deriving

Anton van Straaten anton at appsolutions.com
Tue Apr 8 10:57:11 EDT 2008

Hans Aberg wrote:
> On 8 Apr 2008, at 16:32, Anton van Straaten wrote:
>>> There are two processes here: deriving, i.e., inheriting an 
>>> interface; and instantiating, i.e., producing running code. Haskell 
>>> denotes derivation by "=>". And "data <a> deriving (b_1, ..., b_k)" 
>>> is really a short for
>>>   data <a>
>>>   instance b_1 where <compiler implementation>
>>>   ...
>>>   instance b_k where <compiler implementation>
>>> So "instance" seems the word that should have been used.
>> How about making "deriving x" an expression which means:
>>   instance x where <compiler implementation>
>> This innovative solution will minimize changes to the Haskell 
>> compiler, documentation, and programmer's brains.
> So what is the difference from the current state? 

None.  See how efficient a solution it is?  ;)

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