[gecode-users] Starting with C++

[Javier Andrés Mena Zapata]

Hi Christian,

If one of the reasons, is historical, and supossing you must/want to
reimplement it, then would you implement Gecode using the same design?

If no, then how would you implement it?

Thanks,

On Wed, Nov 19, 2008 at 5:24 AM, Christian Schulte <cschulte at kth.se> wrote:

> Hi Malcolm,
>
> all your questions have a yes as the answer. Having the possibility to
> construct variables in an uninitialized state is actually quite useful
> (think of just declaring an integer variable without initializing, same
> thing). It might not useful during copying but in other situations (in
> particular think of an array of variables - such as IntVarArgs - you would
> like to pass as an argument, here you definitely do not want to create a
> variable first and then overwrite it).
>
> The reason why copying an array is not controlled by a copy constructor but
> by an update function is for two reasons: one, historical (because in
> earlier versions the constructor would have clashed with other
> constructors)
> and the other uniformity (for some data structures it is not very easy to
> define a constructor, but it is easy to have a separate update function).
>
> Cheers
> Christian
>
> --
> Christian Schulte, www.ict.kth.se/~cschulte/<http://www.ict.kth.se/%7Ecschulte/>
>
>
> -----Original Message-----
> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
> Of Malcolm Ryan
> Sent: Wednesday, November 19, 2008 5:06 AM
> To: gecode list
> Subject: [gecode-users] Starting with C++
>
> Given that GecodeJ is no longer supported, I'm in the process of
> migrating my code to C++ (and learning C++ in the process).
>
> It seems from my perusal of the examples that the C++ library works
> slightly differently. Whereas in java the copy constructors for spaces
> look like:
>
>   public Queens(Boolean share, Queens queens) {
>     super(share, queens);
>     n = queens.n;
>     q = new VarArray<IntVar>(this, share, queens.q);
>   }
>
> in C++ they look like:
>
>   /// Constructor for cloning \a s
>   Queens(bool share, Queens& s) : Example(share,s) {
>     q.update(this, share, s.q);
>   }
>
> The Java code explicitly contructs a new var array from the old. The C+
> + code seems to implicitly construct an empty var array and then call
> 'update' to copy the old into the new. Is that correct? Does every
> kind of variable have an no-arg constructor? What is the rationale for
> this choice? It seems that it allows you to construct variables in an
> incompletely initialised state. Is that deliberate?
>
> Malcolm
>
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-- 
"La buena educación, es lo que nos queda cuando se nos olvida todo lo que
nos han enseñado"
    ¿?

Javier Andrés Mena Zapata
http://StrategicDecision.net/
+57 (2) 318 1000 ext. 2910
Cali - Colombia
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