[Haskell-cafe] Re: What I wish someone had told me...

John Lato jwlato at gmail.com
Wed Oct 15 06:06:21 EDT 2008

> Albet Lai wrote:
> John Lato wrote:
>> Are you advocating introducing existential types to beginning
>> Haskellers?  I think something with the scary name "existential
>> quantification" would greatly increase the head'splodin' on the
>> learnin' slope.
> OOP(*) advocates introducing existential types to beginning programmers.

Yes, because they're required to get almost anything done in OOP
languages.  In general they are not required in Haskell.  I got a bit
carried away with rhetorical flourish, but my point wasn't so much
that beginners couldn't understand something as that something with
such specialized usage isn't necessary for new Haskellers, and is
likely to encourage bad habits from OOP-converts.

> The broken analogy between OOP interfaces and Haskell/Isabell type
> classes is there because some people insist that all languages should be
> like mainstream languages. You have heard it, even from reputable
> leaders and pioneers: "if you know one language, picking up others
> should be easy, they just differ in syntax".

I have heard it, and I used to believe it.  Now I think it's only true
provided the one language you know is suitably advanced (and currently
non-existent, I think).


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