Give helpfull error on - or / of meshes

[fipymigrate]

When translating meshes, one cannot do

mesh = Grid2D(dx=dx, dy=dy, nx=nxtot, ny=nytot) - [[Lval/2], [0]]

but must do

mesh = Grid2D(dx=dx, dy=dy, nx=nxtot, ny=nytot) + [[-Lval/2], [0]]

The error given in the first case is not very helpfull for unexperience users:

TypeError: unsupported operand type(s) for -: 'instance' and 'list'

The patch in attachment adds sub and div and gives helpfull error message in those cases.

Imported from trac ticket #299, created by benny.malengier@gmail.com on 06-29-2010 at 09:32, last modified: 10-11-2011 at 15:59

[fipymigrate]

benny.malengier@gmail.com attached minus.patch on 06-29-2010 at 09:32

[wd15]

Fixed with r4761

Trac comment by wd15 on 09-20-2011 at 15:18

[guyer]

I agree that the previous error wasn't very helpful, but wouldn't it be better to just support the operations instead of raising a slightly clearer error?

Trac comment by guyer on 09-20-2011 at 18:22

[wd15]

sub does work now. Line
trunk/fipy/meshes/abstractMesh.py#L917 dealt with that.

>>> from fipy import *
>>> print (Grid1D() - [[1]]).cellCenters
[[-0.5]]

Trac comment by wd15 on 10-07-2011 at 15:50

[wd15]

Added div method with r299. Closing.

Trac comment by wd15 on 10-11-2011 at 15:58

[wd15]

Replying to wd15:

Added div method with r4805. Closing.

Trac comment by wd15 on 10-11-2011 at 15:59