Can GenericFunctions not be interpolated?

Question

Is there a deeper reason why GenericFunctions cannot be interpolated?

from dolfin import *

f = Expression('sin(x[0])')

mesh = UnitSquareMesh(20, 20)
V = FunctionSpace(mesh, 'CG', 1)

u = Function(V)
u.interpolate(f) # no problemo

u.interpolate(2 * f) # mööp

I'd like to avoid the projection step here.

Comments

Actually GenericFunction can be interpolated but 2 * f is not GenericFunction but it is UFL something.

Answer 1

In the development version of FEniCS (DOLFIN) you can create an Expression from any scalar GenericFunction. So your last line could be exchanged with:

u.interpolate(Expression("2 * f", f=f))