Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Manipulate and Initialization
Replies: 0

 Simons, F.H. Posts: 107 Registered: 12/7/04
Manipulate and Initialization
Posted: Mar 23, 2013 3:24 AM

I want to create a rather complicated Manipulate, in which I do not know
the limits for the parameter beforehand; they depend on the result of an
initialization. Here is a highly simplfied example:

Clear[nn];
Manipulate[n, {n,1,nn,1},
Initialization:>(nn=RandomInteger[{5,15}];Print[nn])]

This works fine. The slider can be used in the range from 1 to the
printed value.

However, when nn already has a value, the behaviour is different. When
we execute

nn=23;
Manipulate[n, {n,1,nn,1},
Initialization:>(nn=RandomInteger[{5,15}];Print[nn])]

a value between 5 and 15 for nn is printed, but that value is not used
in the result; the slider now runs from 1 to 23.

So, whether nn has a value or not, just before the box structure is
printed, the frontend asks the kernel to evaluate the initialization.
But the returned value of nn is used in Manipulate only when nn did not
have a value before. That embarasses me. Any explanation is highly
apprectiated.

Fred Simons
Eindhoven University of Technology