[Haskell-beginners] Haskell-style types in C or C++

[Alexander Batischev]

Hi!

On Sat, Jul 30, 2011 at 10:45:06AM -0800, Christopher Howard wrote:
> One of the things that I love about Haskell is the syntax for
> creating user defined types. E.g.:
> 
> Data QueryResult = NoResult | DatabaseError String | Results [String]
> 
> I can prototype an entire program around these self-made types and
> it is a lot of fun. Out of intellect curiosity, though: what would
> be the equivalent construction in C or C++? (Say, for the type
> defined above).

Recently, same question occurred to me too, and the only solution I
could think of is defining base class (analog of data type name,
QueryResult in your case) and creating subclasses for each of data type'
constructors (NoResult, DatabaseError, Results). And you should resort
to templates if you want something like [a] as a parameter.

Google provides few nice links [1] [2] which may be helpful.

Just for your information, types like in the example above are called
Algebraic Data Types (ADT).

  1. http://cpp-next.com/archive/2010/09/algebraic-data-types-in-c/
  2. http://stackoverflow.com/questions/16770/haskells-algebraic-data-types

-- 
Regards,
Alexander Batischev

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