88 lines
2.1 KiB
Markdown
88 lines
2.1 KiB
Markdown
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GTSAM Concepts
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==============
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Concepts define (see [Generic Programming Techniques](http://www.boost.org/community/generic_programming.html))
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* associated types
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* valid expressions
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* invariants
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* complexity guarantees
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GTSAM Types start with Uppercase, e.g., `gtsam::Point2`, and are models of the concepts MANIFOLD, GROUP, LIE_GROUP, VECTOR_SPACE
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`gtsam::traits` is our way to associate these concepts with types. We will not use Eigen-style or STL-style traits, that define many properties at once. Rather, we use boost::mpl style meta-programming functions to facilitate meta-programming.
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Traits allow us to play with types that are outside GTSAM control, e.g., `Eigen::VectorXd`.
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The naming conventions are as follows:
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* Types: `gtsam::traits::SomeAssociatedType<T>::type`, i.e., they are MixedCase and define a `type`, for example:
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template<>
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gtsam::traits::TangentVector<Point2> {
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typedef Vector2 type;
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}
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* Values: `gtsam::traits::someValue<T>::value`, i.e., they are mixedCase starting with a lowercase letter and define a `value`, but also a `value_type`. For example:
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template<>
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gtsam::traits::dimension<Point2> {
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static const int value = 2;
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typedef const int value_type; // const ?
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}
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* Functors: `gtsam::traits::someFunctor<T>`, i.e., they are mixedCase starting with a lowercase letter and define a functor type
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template<>
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gtsam::traits::retract<Point2> {
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Point2 operator()(const Point2& p, const Vector2& v) {
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return Point2(p.x()+v[0], p.y()+v[1]);
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}
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}
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The above is still up in the air, can we not point to a function somewhere? Or a method?
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Concepts are associated with a tag.
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Manifold
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--------
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`gtsam::tags::manifold_tag`
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`gtsam::traits::structure_tag<T>`
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* associated types: DefaultChart
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* valid expressions: dimension
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Chart
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-----
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Group
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-----
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Lie Group
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---------
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Vector Space
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------------
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Examples
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--------
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An example of implementing a Manifold is here:
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namespace gtsam {
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namespace traits {
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// types:
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template<typename T>
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struct SomeAssociatedType<T>::type
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}
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}
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