Once you have created an element, you may want to give it a value, that can depends on a lot of parameters ( mainly spaces, but others may apply ).
To do so, Feel++ relies on expressions. We may use various kind of expressions :
Let’s begin with the evaluation of the expression \$sin(\pi x)\$ on a unit circle.
First at all, we define the unit circle and its function space :
link:{examplesdir}/05-myexporter.cpp[role=include]Then the expression we would like to evaluate :
link:{examplesdir}/05-myexporter.cpp[role=include]Px() refers to the variable x of our space.
With this,we can project it on our function space :
link:{examplesdir}/05-myexporter.cpp[role=include]The expression will be evaluated on each point of our mesh.
In order to visualize the result, we create an exporter, named exhi, and add to it the projection.
link:{examplesdir}/05-myexporter.cpp[role=include]In this second method, we will use Functor :
link:{examplesdir}/myfunctor.cpp[role=include]We create a unit square meshed by triangles and we define the associated function space :
link:{examplesdir}/myfunctor.cpp[role=include]From this space, we can define two elements, here one equals to the
variable \$x\$ and the other to the variable \$y\$, obtain from
Functor class.
link:{examplesdir}/myfunctor.cpp[role=include]The data exportation is the final step to visualize our expression \$x\$ and \$y\$ on the defined mesh.
link:{examplesdir}/myfunctor.cpp[role=include]