c++ and ublas: creating an array of c_vectors with different sizes

Question

Is there a way to create an array of ublas c_vectors with different sizes?

For example

array[0] would return an ublas::c_vector< double, 3 > (size=3) and array[0](0) would access its first element

array[1] would return an ublas::c_vector< double, 7 > (size=7) and array[1](0) would access its first element

etc

[If you want it to be a possessive...](http://www.homestarrunner.com/sbemail89.html) — Kerrek SB, Sep 19 '11 at 20:14
No problem. Using the backticks for code is especially important if you have those angled brackets, which would otherwise just disappear. — Kerrek SB, Sep 19 '11 at 20:18
@niels: Reading the instructions is especially important when it's your first time! Never understood how "it's my first question" was ever an excuse :/ — Lightness Races in Orbit, Sep 19 '11 at 20:30
@niels: Pretty much always, yes! I make use of FAQs and preview panes, because I am aware that they are presented for a reason. — Lightness Races in Orbit, Sep 19 '11 at 20:35

Nawaz · Accepted Answer · 2011-09-20T04:55:18.043

0

I think you can use std::vector<boost::any>, and then push ublas::c_vector of different sizes into it.

std::vector<boost::any> v;
v.push_back(ublas::c_vector<double,3>());
v.push_back(ublas::c_vector<double,7>());
v.push_back(ublas::c_vector<double,9>());
//etc

Elements should be cast back to the appropriate types, using boost::any_cast which is custom keyword cast for extracting a value of a given type from boost::any.

You could try boost::variant as well. Choose whatever suits your need better. Read this before making a decision:

Boost.Variant vs. Boost.Any

edited Sep 20 '11 at 04:55

answered Sep 19 '11 at 20:14

Nawaz

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That seems to be the only solution, given that vectors of different sizes don't share any common base class. – Kerrek SB Sep 19 '11 at 20:25
I tried this but a get a "call of an object of a class type without appropriate operator() or conversion functions to pointer-to-function" Also tried this 'boost::array v = {ublas::c_vector(), ublas::c_vector()};' and got the same error – niels Sep 19 '11 at 20:27
@KerrekSB: One could use `Variant` as well. But I don't know the exact requirement. – Nawaz Sep 19 '11 at 20:27
@niels: With boost.any, you have to cast the elements back to the required type. I think it's `any_cast` or something like that, but I'm not sure. – Kerrek SB Sep 19 '11 at 21:10
@Kerrek : It is `any_cast`. :-) – Nawaz Sep 20 '11 at 04:52

c++ and ublas: creating an array of c_vectors with different sizes

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