Re: [Haskell-fr] Re: inférence

BIen sur, tu peut utiliser mes questions ;) Et merci pour les réponses! On 9/18/07, Dan Popa wrote:

--- Dupont Corentin wrote:

1)

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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)

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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.

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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'

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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.

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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 french for Haskell-fr ?

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