[with patch; positive review] notebook -- bug; @interact cell eval doesn't clear out the old html output (easy to fix?)

[was]

To replicate this bug:

1. Put show(plot(sin)) in a cell and press shift-enter

2. Then in the *same* cell *delete* show(plot(sin)) and replace it by this and press shift-enter:

   @interact
   def _(n=(1,100)):
      print n^2
   

3. Observe that the plot of sin is still there.

[boothby]

The following is now broken:

plot(sin,0,1).show()
@interact
def foo(a="1"):
    a

[was]

Hi,

Your only reason for giving a negative review was a claim that

plot(sin,0,1).show()
@interact
def foo(a="1"):
    a

is now "broken". However, this never did what you thought it did. The behavior in fact hasn't changed at all from how it was before, except to remove the bug where old graphics from the previous version of the cell remained.

@interact *by design* is only supposed to work when it is the only thing in a cell.

Having multiple interacts in a cell, having additional graphics in a cell, having nested interacts -- none of that should work at present, since none of it has been implemented. They're all things that would possibly be very nice to implement, but they were not part of the design goals for the first version of interact.

[boothby]

It was not clear to me, even upon rereading the documentation, that @interact had to be alone in a cell. The attached "fixes" the issue. :)

[mabshoff]

Merged both patches in Sage 3.0.2.alpha1