Just do the following:

Mesh mesh; Function f;

real* vertex_values = new real[mesh.numVertices()];
f.interpolate(vertex_values);

Then vertex_values will be an array with the values at all vertices.

For a scalar function, you simply get all the vertex values and for a 
vector (or in general tensor-valued) function, you first get all the 
values for component 0, then all values for component 1 etc.

/Anders


Alessio Quaglino wrote:
>> On Tue, Jun 26, 2007 at 02:56:52PM +0200, Alessio Quaglino wrote:
>>> I'm trying to get my code working with the new dolfin 0.7.0-1 but it
>>> seems
>>> there are a several problems. For example, a part of the
>>> dolfin::Function
>>> interface has disappeared. In particular, it is not possible to get the
>>> value corresponding to a vertex or the finite element space where the
>>> function is living. Have these functionalities been moved somewhere
>>> else?
>>>
>>> Regards,
>>> Alessio Quaglino
>> Use Function::interpolate() to access the values. Often, one can
>> avoid ever needing to access the values directly, but if they should
>> be needed, then it is possible to either interpolate the Function to a
>> given Cell (getting the expansion coefficients in the local finite
>> element basis) or get the values at all vertices.
>>
>> So, try to avoid accessing the values but if you really need the
>> values at vertices you can still get them.
>>
>> /Anders
>> _______________________________________________
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> 
> Ok I see, however with interpolate() I can either get all the Vertex
> values or the values at a given Cell. While the latter case is unefficient
> for my purpose  because I'd pass through the same Vertex several times, in
> the former I get a vector with the values at all vertices but no
> information about how to access such a vector.
> 
> Regards,
> Alessio
> 
> 
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