Re: [Haskell-cafe] Re: Datatypes - Haskell

On Feb 10, 2008 3:40 PM, Mattes Simeon wrote:

Thanks for your help. It was very useful.

Though in comparison with C or C++ I can't figure out so clear the syntax. Maybe it has to do with the syntactic Sugar of each Language. I 'll give you a similar example I saw in a book for Haskel

The following program just returns the value of the position of a datatype Tuple which can hold one or two elements.

data Tuple a b = One a | Two a b tuple1 (One a)= Just a tuple1 (Two a b) = Just a

tuple2 (One a) = Nothing tuple2 (Two a b) = Just b

The corresponding Version in C++, which seems to be more appropriate, would be

I think this is the most native way to do it in C++: template class Tuple { public: static Tuple *One (A *a) { return new One (a); } static Tuple *Two (A *a, B *b) { return new Two (a, b); } virtual A *tuple1 () = 0; virtual B *tuple2 () = 0; }; template class One : Tuple { public: One (A *a) { this->a = a; } A *tuple1 () { return a; } B *tuple2 () { return NULL; } private: A *a; } template class Two: Tuple { public: Two (A *a, B *b) { this->a = a; this->b = b} A *tuple1 () { return a; } B *tuple2 () { return b; } private: A *a; B *b; } -- vir http://vir.comtv.ru/