Re: [eigen] How to resize a partially fixed matrix

[Patrick Mihelich <patrick.mihelich@xxxxxxxxx>]

The syntax is inherited from C; it just looks weird because the brackets are empty. But I was being too clever earlier. We don't need static initialization here since it's just the type we care about. Here's a more sensible version:

struct NoChange_t {};
namespace {
  NoChange_t NoChange;
}

The anonymous namespace avoids multiple definition troubles.

Cheers,
Patrick

On Wed, Jun 24, 2009 at 3:52 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:

2009/6/24 Patrick Mihelich <patrick.mihelich@xxxxxxxxx>:

> I like the NoChange API, but I get a little leery seeing overloads
> disambiguated on integral types (even though it seems OK here). A safe
> approach in general is to use a statically initialized tag object, that is
> change
>
> enum NoChange_t { NoChange };
>
> to
>
> struct NoChange_t {} NoChange = {};

Hehe, that's why I initially proposed an approach with a struct
NoChange... but I retracted it because I was afraid of "multiply
defined object" issues as this is in a header file. I'll be honest: I
didn't know about the C++ syntax that you propose here. Do you confirm
it's standard c++98, and takes care of the "multiply defined object"
issue? If yes i'm all for your solution.

Cheers,
Benoit

>
> Cheers,
> Patrick
>
> On Wed, Jun 24, 2009 at 1:37 PM, Markus <grey_earl@xxxxxx> wrote:
>>
>> Am Mittwoch, 24. Juni 2009 schrieb Benoit Jacob:
>> > First of all the variant proposed:
>> > >> So I'm strongly for your code change, but changing the assertion to
>> > >> EIGEN_STATIC_ASSERT_EXACTLY_ONE_DYNAMIC_DIM(Matrix)
>> >
>> > doesn't make me comfortable, again because a method that works for
>> > (partially)dynamic matrices should also work on fixed-size matrices of
>> > the same size, I am very reluctant here.
>> >
>> > So here's what I did (changeset b030f9866bae):
>> >     * add resize(int, NoChange) and resize(NoChange, int)
>> >     * add missing assert in resize(int)
>> >     * add examples for all resize variants
>> >     * expand docs (part of which is from Tim Hutt's e-mail)
>> >
>> > Now if you want we can add another name (or completely rename) the new
>> > resize(int, NoChange) and resize(NoChange, int).
>> > But perhaps it's good enough like this? i don't have a strong opinion.
>> > resizeHoriz(size) and colwise().resize(size) look nice but they aren't
>> > much shorter to type than resize(NoChange,size);
>> >
>> > Cheers,
>> > Benoit
>> >
>>
>> Does this also work for fully dynamic matrices now?
>>
>> So if I have
>>
>> Matrix<double, Dynamic, Dynamic> mat;
>> mat.resize(3,3);
>> mat.resize(NoChange, 5);
>>
>> does this work? If yes, everything fine with me.
>>
>> Markus
>>
>>
>
>