Actually, I just came up with a simpler idea: rather than creating a
new iterator class, you could simply use a pointer as the iterator type,
so that adding a full set of begin()/end() methods is easy:
#include <iterator> // STL iterator classes
template<class Var> VarArray {
protected:
int n;
Var* v;
public:
Var* VarArray::begin() { return v; }
Var* VarArray::end() { return v+n; }
const Var* VarArray::begin() const { return v; }
const Var* VarArray::end() const { return v+n; }
Var* VarArray::rbegin() { return std::reverse_iterator(end()); }
Var* VarArray::rend() { return std::reverse_iterator(begin()); }
const Var* VarArray::rbegin() const { return
std::reverse_iterator(end()); }
const Var* VarArray::rend() const { return
std::reverse_iterator(begin()); }
...
};
(And of course the same can be done for ArgArrayBase.)
Adding these methods should be sufficient to allow library users to
iterate over your arrays using the standard idioms.
Cheers,
Greg
On 1/17/11 5:47 AM, Christian Schulte wrote:
Hi,
Yes, this list is a good forum...
Again you caught us red-handed... I know that begin() and end() is the
standard idiom but some of our iterators do not naturally fit in this
concept (that iterators that iterate over values and ranges of variables and
views).
I think what one could do is providing a wrapper class that translates a
Gecode-style iterator (using a constructor or init function for
initialization, operator ++() for moving to the next element, and operator
()() for testing whether the operator is done). If you can come up with
something like that we would of course integrate it.
Best
Christian
--
Christian Schulte, www.ict.kth.se/~cschulte/
-----Original Message-----
From: Gregory Crosswhite [mailto:[email protected]]
Sent: Monday, January 17, 2011 12:36 AM
To: [email protected]; [email protected]
Subject: Re: [gecode-users] int vs. unsigned int for Matrix dimensions
Part of the reason I am asking how to talk to the developers,
by-the-way, is because I was thinking it might be useful for the
arrays/argument arrays to have an iterator interface added to them, to
make it easier to do things like applying generics algorithms to them
and traversing them using the c++0x "for each" statement as well as
BOOST_FOREACH. Would there be any interest in a contribution to Gecode
to provide this? The supporting code that I had in mind would include
new classes for the iterators and new methods .begin() and .end() for
the arrays.
Cheers,
Greg
On 1/16/11 1:46 PM, Gregory Crosswhite wrote:
Okidoke; thanks for the explanation! :-)
Also, is this list the best way to talk to the developers of Gecode?
Thanks,
Greg
On 1/16/11 1:10 PM, Christian Schulte wrote:
Hi Gregory,
You are touching a slightly weird aspect of Gecode... The choice of
int as
opposed to unsigned int for the Matrix class is actually deliberate.
This
choice is not only done for Matrix but for many other datastructures
that
are defined by Gecode (for example, VarArray, ViewArray, etc). I know
that
the choice of unsigned int sounds more appealing but we have made the
opposite decision and try to be as consistent with the choice of int
rather
than unsigned int.
There are two reasons. The first is simple and maybe is not even very
convincing. The average loop written to iterate over arrays etc is
typically
an int and not an unsigned int. To avoid compiler warnings, Gecode
follows
in this. Then, the second reason (possibly not more convincing than the
first one) is that integer variables take int values and very often
array
access is wrt a value included in the domain of an integer variable.
Here we
go.
We tried to use unsigned int but it was in fact just too painful
(lots of
explicit casts in order to avoid warnings). Changing int to unsigned
int and
be consistent about that change would be a massive effort with little
gain.
I know. Sad but true.
Cheers
Christian
--
Christian Schulte, web.ict.kth.se/~cschulte/
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf
Of Gregory Crosswhite
Sent: Friday, January 14, 2011 6:26 PM
To: [email protected]
Subject: [gecode-users] int vs. unsigned int for Matrix dimensions
Hey everyone,
Is there a reason why the Matrix class uses "int" for the type of its
dimensions instead of "unsigned int"? If there isn't a reason not to
use "unsigned int" for the type of the dimensions, then may I submit a
patch or something to change it to use "unsigned int"?
Thanks!
Greg
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