Dupont Corentin corentin.dupont at gmail.com
Thu Sep 20 08:47:19 EDT 2007

```BIen sur, tu peut utiliser mes questions ;)
Et merci pour les réponses!

On 9/18/07, Dan Popa <popavdan at yahoo.com> wrote:
>
> --- Dupont Corentin <corentin.dupont at gmail.com> wrote:
>
> 1)
> > Salut,
> >
> > Personne ne peut me répondre sur mon erreur
> > ci-dessous?
> > comment caster de Float en Double?
> >
> If you really need a datatype for a Point you may use
> something like :
>
> Num a => Point a a
>
> specifying that:
> I) a may be every numeric type and
> II) a point is something which includes 2 pieces of
> date which belongs to that type  a.
> As a result the system will use the needed kind of
> points everywhere.
>
>
> 2)
> > J'ai d'autres questions:
> > Je n'ai pas très bien compris ce que signifie le '.
> > Apparemment ça a à voir avec l'impératif...
>
> Nothing special. It is like _ in other languages.
>
> > Je ne comprend pas très bien ce que font des
> > opérateurs comme &&&:
> > (&&&) :: (Arrow a) => a b c -> a b c' -> a b (c, c')
> Translation: In the hypothesis that a is a type froma
> a class of types called Arrow then the type of the &&&
> function (operator) is: a b c -> a b c' -> a b (c, c')
>
> Remark: you may presume that  a and b are  type
> constructors (like m for monads).
> So:
> a b c means: the a type constructor applied to ( b
> type constructor applied to a data fromthe type c).
> This is a complex datatype.
> a b c' means:  the a type constructor applied to ( b
> type constructor applied to a data the type c'). This
> is a complex datatype. c' may or may not be the same
> with c.
>
> a b (c, c') means: the a type constructor applied to (
> b type constructor applied to the pair formed by last
> c and last c'). This is a complex datatype. c' may or
> may not be the same with c but both are the previously
> c and c', now alltogether.
>
> (c,c') means: pair made by c and c'
>
> > Dans la signature, que signifient les espaces entre
> > les a,b,c...?
>
> Application of the typeconstructor from the left to
> the  datatype from the right. It's something like:
> a(b(c)) in mathematics.
> >
> > Merci!
> > Corentin
>
> You are wellcome !
> Dan
>
> P.S. Can I use the question rised, for example as
> examples for my students or by posting them to
> haskell.org in any language ?
>
> Or would you like to translate the explanations in