Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-11 Thread Frank Atanassow
On Jun 9, 2004, at 9:39 AM, Jerzy Karczmarczuk wrote: I have *nothing* to add, just a question. Do you /anybody/ know of any edible work on ADJUNCTIONS in the context of Haskell structures? Perhaps instead of searching for 'inverses' one should think more about adjoints?... Yes, I think this is t

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-10 Thread Benjamin Franksen
On Wednesday 09 June 2004 17:20, Ron de Bruijn wrote: > --- "Iavor S. Diatchki" <[EMAIL PROTECTED]> wrote: > Only I still find it weird that join is called a > multiplication, because according to the definition of > multiplication, there should be an inverse. I think, > thus that multiplication is

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread ajb
G'day all. Quoting Ron de Bruijn <[EMAIL PROTECTED]>: > I have thought a while about morphisms and although I > had written down in my paper that a functor and also a > natural transformation are also morphisms, but in a > different category, I now am not sure anymore of this. It's true. In par

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread ajb
G'day all. Quoting Rik van Ginneken <[EMAIL PROTECTED]>: > It is more even subtle if one considers the rotation group. > The unit is keeping an object on its place. > The multiplication is doing rotations sequently. > Allright, one has an inverse here, but > the rule (a*b)*c = a*(b*c) doesn't occ

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread Ron de Bruijn
Hello again, I have thought a while about morphisms and although I had written down in my paper that a functor and also a natural transformation are also morphisms, but in a different category, I now am not sure anymore of this. If you see everything(objects and morphisms) as dots and arrows, an

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread Graham Klyne
At 08:20 09/06/04 -0700, Ron de Bruijn wrote: Only I still find it weird that join is called a multiplication, because according to the definition of multiplication, there should be an inverse. For real or rational numbers, maybe. But also think about Integers, or matrices. [ 1 2 ] * [ 3 ] = [ 11

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread Rik van Ginneken
?! I found out what a group is: ?! A group is a monoid each of whose elements is ?! invertible. ?! OK. ?! Only I still find it weird that join is called a ?! multiplication, because according to the definition of ?! multiplication, there should be an inverse. I think, No, it ain't. If you ta

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread Ron de Bruijn
--- "Iavor S. Diatchki" <[EMAIL PROTECTED]> wrote: > hi ron, > > here are the relations between the two formulations > of monads: > (using haskell notation) > > map f m = m >>= (return . f) > join m = m >>= id > > m >>= f = join (fmap f m) > > there are quite a few general co

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-09 Thread Jerzy Karczmarczuk
Iavor S. Diatchki wrote: Ron de Bruijn wrote: I am pretty sure, that >>= is to monads what * is to for example natural numbers, but I don't know what the inverse of >>= is. And I can't really find it anywhere on the web(papers, websites, not a single sole does mention it. this is not quie correc

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-08 Thread Iavor S. Diatchki
hi ron, here are the relations between the two formulations of monads: (using haskell notation) map f m = m >>= (return . f) join m = m >>= id m >>= f = join (fmap f m) there are quite a few general concepts that you need to understand in what sense monads are monoids, but to unde

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-08 Thread Ron de Bruijn
I am pretty sure, that >>= is to monads what * is to for example natural numbers, but I don't know what the inverse of >>= is. And I can't really find it anywhere on the web(papers, websites, not a single sole does mention it. It should have type, at least that's what I think: inv::M a->M b I sa

Re: [Haskell-cafe] Join and it's relation to >>= and return

2004-06-07 Thread Scott Turner
On 2004 June 07 Monday 15:19, Ron de Bruijn wrote: > newtype S a = State -> (a,State) -- functor T to map > objects > mapS::(a-> b) -> (S a -> S b) -- functor T to map > morphisms > unitS :: a -> S a --\eta > joinS::S(S a)-> S a -- \mu > > This is a complete monad using a direct mapping from > Ca

[Haskell-cafe] Join and it's relation to >>= and return

2004-06-07 Thread Ron de Bruijn
Hello, The last 3 or 4 days I have been studying a lot of Category Theory so that I would be able to explain the concept of a monad to some people at the university in a "learn to present something"-course. newtype S a = State -> (a,State) -- functor T to map objects mapS::(a-> b) -> (S a -> S