# DataTypes

As you may know, many SOFA C++ classes are templated. The different templates can be found in the page about state vectors and templates. In the code, the use of templates implies the many types in the C++ variable, that are not always easy to understand. This page provides a short introduction to all these types.

All following types are defined from the DataTypes class, and can therefore be used by writing: **DataTypes::MyType**.

**Real**: corresponds to a double or float value, depending on the DataTypes used: a class templated in Vec3d will return a double, whereas a a class templated in Vec3f will return a float

**Coord**: standing for "coordinate", corresponds to a vector of *Real* with a size given by the number of degrees of freedom: a class templated in Vec6d will return a vector of 6 doubles. This vector is homogeneous to your degrees of freedom.

**Deriv** standing for "derivative", corresponds to a vector of *Real* with a size given by the number of degrees of freedom: a class templated in Vec6d will return a vector of 6 doubles

**VecCoord** or **VecDeriv**: corresponds to a vector of respectively *Coord* or *Deriv*

**DataVecCoord or DataVecDeriv**: corresponds to a Data containing a vector of respectively *Coord* or *Deriv*. As noted in the assocaited article, the Data are variable of the class exposed to the user and other components in the scene

**MatrixCoord or MatrixDeriv**: corresponds to a matrix of respectively *Coord* or *Deriv*, this is more especially used by solvers and constraint algorithms

**VecCoordId, VecDerivId, MatrixCoordId or MatrixDerivId**: corresponds to an identifiant value (int) pointing to a vector or matrix of respectively *Coord* or *Deriv*. This is very useful to access specific vectors or matrix in the simulation. State vectors for instance are managed with specific protected Ids by the solvers

Last modified: 5 October 2018