Define the trace operator

Hi !

Is there a way or a predefined function to define the trace operator ? For a given fem function u, I would like to define its restriction to the boundary.

Thank you.

If your function is u, on a fespace Vh, then you can do:

Vh tr;
varf vTrace(unused, v) = on(boundary, unused = u);
tr[] = vTrace(0, Vh, tgv = -1);
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