This PR refactors DQ's default constructor

[ffasilva]

Hi @dqrobotics/developers,

This PR removes DQ's obsolete constructor with default double parameters and adds a new default constructor that takes no arguments, as discussed in #68. The implementation follows Murilo's clever workaround to deprecate the construction, namely:

DQ() noexcept;

[[deprecated("Consider explicitly initializing dual quaternions using the "
             "operators DQ::i_, DQ::j_, DQ::k_, DQ::E_. Alternatively, "
             "use the constructor DQ::DQ(const VectorXd& v) instead.")]]
explicit DQ(const double& q0,
            const double& q1=0.0,
            const double& q2=0.0,
            const double& q3=0.0,
            const double& q4=0.0,
            const double& q5=0.0,
            const double& q6=0.0,
            const double& q7=0.0) noexcept;

Additionally, this PR refactored the internal classes to comply with the new constructor and avoid deprecation warning spam from the library, e.g.,

DQ_MobileBase::DQ_MobileBase()
{
    // -- frame_displacement_ = DQ(1);
    frame_displacement_ = DQ((Matrix<double,8,1>() << 1,0,0,0,0,0,0,0).finished());
}

Usage

#include <dqrobotics/DQ.h>

DQ_robotics::DQ x;
cout << "x = " << x << endl;

x = 0

Kind regards,
Frederico

[mmmarinho]

Hi @ffasilva,

This is nice. I think this mostly fixes the problem, but with this, the cpp version of the library would become the most verbose way possible of writing scalars (as if cpp isn't verbose enough by itself). Using 1 as an example, we previously could write

DQ one(1); 

would become, as you correctly noticed,

auto one = DQ((Matrix<double,8,1>() << 1,0,0,0,0,0,0,0).finished());

Do you think we could work around that with a std::initializer_list constructor? For instance, so that we could do

DQ one({1}); //1
DQ p({1,2,3}); //i_ + 2*j_ + 3*k_
DQ r({0,1,0,0}); //j_

This might require some combinations of creating this new initializer list and further modifying the previous constructor in the way I suggested in #68.

[ffasilva]

Hi @mmmarinho,

I'm also not entirely happy with how verbose it is to initialize scalars now. Thanks for the suggestion! I'm marking this PR as a draft while I check it.

Kind regards,
Frederico