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

[Tim Hutt <tdhutt@xxxxxxxxx>]

2009/6/24 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> 2009/6/24 Markus Benjamin Fröb <grey_earl@xxxxxx>:
>>>     Matrix<float,Dynamic,2> m;
>>>     m.resize(3);
>>>
>>> but then we also want this to work:
>>>
>>>     Matrix<float,3,2> m;
>>>     m.resize(3);
>>
>> I don't see why the second case should work, since a) it's ambigous what the
>> user wanted and b) in the documentation it says explicitly "Of course, fixed-
>> size matrices can't be resized."
>
> Yes, that's what I meant, sorry if I was unclear, we were wondering if
> A should be allowed and I said "if we want to allow A then we also
> want to allow B", where B is impossible, conclusion: we can't allow A.

I see what you mean. You're saying if you have code like this:

Matrix<double, Dynamic, 3> m;
// ... lots of code ...
m.resize(10, 3);

And then for some reason later you want to make m fully dynamic then
you only have to change the declaration:

Matrix<double, Dynamic, Dynamic> m;
// ... lots of code ...
m.resize(10, 3); // Still works.

In which case the trade-off is:

Pros: Constructor and resize are more logical, code is less redundant.
The code shows that the matrix isn't fully dynamic (i.e. you might
accidentally try m.resize(10, 4) in the code above.
Cons: Have to change code if you change matrices from partially to
fully dynamic.

Tim