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[Jake Ostien <tostien@xxxxxxxxx>]

Hi,

This seems like it should be easy, so I am sorry I have to ask. 

How do I set a simple support (i.e. fixed dof in x, free dof in y) in a 
2D elasticity problem.  I have figured out how to do it if I am weakly 
enforcing Dirichlet BC's in a DG formulation, but I can't figure out how 
to do it for the classical formulation using BoundaryConditions.

Here is what I have tried (among other things) using pieces of code from 
the elasticity demo, but for 2D...

.
.
.
Clamp c(mesh);
Function cx = c[0];
Left left;
BoundaryCondition bcl(cx, mesh, left);
.
.
.

But I get an error that says

terminate called after throwing an instance of 'std::runtime_error'
 what():  *** Error: Sub functions can only be extracted from discrete 
functions.
Aborted


After nosing around a bit, its not clear if I need to create a SubSystem 
or not, but I think I would run into the same problem as above.
Any suggestions will be appreciated.

-Jake