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[Anders Logg <question105900@xxxxxxxxxxxxxxxxxxxxx>]

Question #105900 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/105900

    Status: Open => Answered

Anders Logg proposed the following answer:
On Wed, Mar 31, 2010 at 09:21:50AM -0000, Chris Richardson wrote:
> Question #105900 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/105900
>
>     Status: Answered => Open
>
> Chris Richardson is still having a problem:
>
> I still don't really understand why you need the extra qualification in these statements. Surely, the boundary
> would be equally well defined without the x[1] clauses. Why do I need to put in the x[1] range so exactly?
>
>
>    left = x[0] < DOLFIN_EPS and (x[1] > DOLFIN_EPS
>                                       and x[1] < 1.0 - DOLFIN_EPS)

If you don't include x[1] here, you will include the points (0, 0) and
(0, 1). That means those point will be in "left" and thus

  return on_boundary and not (left or right)

will return false for those points. I assume you want to include those
points in a no-slip boundary condition or similar.

>         right = abs(x[0] - 1.0) < DOLFIN_EPS and (abs(x[1] - .5) > DOLFIN_EPS
>                                                   and x[1] < 2.0 - DOLFIN_EPS)

This looks strange. What does x[1] range mean here?

--
Anders

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