Integrals Integrate Describe the `integrate()` primitive and how to use it to compute integrals and assemble forms. Mean Compute the mean value of a function using the `mean()` helper. Norms Helpers to compute common norms (L2, H1, Linf) and related interfaces. Boundary integrals Integrals computed on mesh boundaries and marked faces (fluxes, boundary contributions). Integrals on subdomains Integrals restricted to marked subdomains or regions in a mesh.