[Haskell-cafe] Re: Theory about uncurried functions
Peter Verswyvelen
bugfact at gmail.com
Thu Mar 5 07:09:46 EST 2009
Ha. There's even a wiki page on the paradoxes of set theory
http://en.wikipedia.org/wiki/Paradoxes_of_set_theory
If I recall correctly, a math professor once told me that it is not yet
proven if the cardinality of the power set of the natural numbers is larger
or smaller or equal than the cardinality of the real numbers... But that is
many many years ago so don't shoot me if I'm wrong :)
2009/3/4 Luke Palmer <lrpalmer at gmail.com>
> On Wed, Mar 4, 2009 at 3:38 PM, Achim Schneider <barsoap at web.de> wrote:
>
>> There's not much to understand about CT, anyway: It's actually nearly
>> as trivial as set theory.
>
>
> You mean that theory which predicts the existence of infinitely many
> infinities; in fact for any cardinal, there are at least that many
> cardinals? That theory in which aleph_1 and 2^aleph_0 are definitely
> comparable, but we provably cannot compare them? The theory which has
> omega_0 < omega_1 < omega_2 < ... omega_omega < ..., where obviously omega_a
> is much larger than a... except for when it catches its tail and omega_alpha
> = alpha for some crazy-ass alpha.
>
> I don't think set theory is trivial in the least. I think it is
> complicated, convoluted, often anti-intuitive and nonconstructive.
>
> Category theory is much more trivial, and that's what makes it powerful.
> (Although training yourself to think categorically is quite difficult, I'm
> finding)
>
>
>
>> One part of the benefit starts when you begin
>> to categorise different kind of categories, in the same way that
>> understanding monads is easiest if you just consider their difference
>> to applicative functors. It's a system inviting you to tackle a problem
>> with scrutiny, neither tempting you to generalise way beyond
>> computability, nor burdening you with formal proof requirements or
>> shackling you to some other ball and chain.
>>
>> Sadly, almost all texts about CT are absolutely useless: They
>> tend to focus either on pure mathematical abstraction, lacking
>> applicability, or tell you the story for a particular application of CT
>> to a specific topic, loosing themselves in detail without providing the
>> bigger picture. That's why I liked that Rosetta stone paper so much: I
>> still don't understand anything more about physics, but I see how
>> working inside a category with specific features and limitations is the
>> exact right thing to do for those guys, and why you wouldn't want to do
>> a PL that works in the same category.
>>
>>
>> Throwing lambda calculus at a problem that doesn't happen to be a DSL
>> or some other language of some sort is a bad idea. I seem to understand
>> that for some time now, being especially fond of automata[1] to model
>> autonomous, interacting agents, but CT made me grok it. The future will
>> show how far it will pull my thinking out of the Turing tarpit.
>>
>>
>> [1] Which aren't, at all, objects. Finite automata don't go bottom in
>> any case, at least not if you don't happen to shoot them and their
>> health drops below zero.
>>
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