What does _mlans24 mean when using the symbolic toolkit?

If I do the following, I get an interesting error. What I'm trying is directly out of the documentation.

EDU>> syms x EDU>> int(x*log(1 + x), 0, 1)

ans =

_mlans24

Thanks,

Mark

Answer 1

[Walter Roberson]

Please try again from a fresh session. There is a possibility that you had some kind of constraint against x. Constraints against symbols are not removed by assigning new values to the symbols at the matlab level.

I must admit I'm having trouble figuring out what it might be trying to convey there. The 24 would be an arbitrary instance number, and the _mlans would be conveying information about the type of the value... but I do not recognize anything close to mlans as a description of a type.

Which version are you using?

[Mark]

That is interesting, restarting the session fixed it, at least for that example.

I am using MATLAB 2010a Student, 32-bit Windows.

I ended up trying a more complicated example, it took a long time, and so I used ctrl-C to stop it. Then the next time I try to use int I get:

_mlans175

So I suspect there is something like you suggest is happening where constraints are being set (not deliberately by me though), and then subsequently causing this problem.

[Walter Roberson]

http://www.mathworks.com/products/optimization/demos.html?file=/products/demos/shipping/optim/symbolic_optim_demo.html

Cleaning Up Symbolic Variables

The symbolic variables used in this demo were assumed to be real. To clear this assumption from the symbolic engine workspace, it is not sufficient to delete the variables. You must either clear the variables using the syntax

syms x1 x2 clear

or reset the symbolic engine using the command

% reset(symengine) % uncomment this line to reset the engine

After resetting the symbolic engine you should clear all symbolic variables from the MATLAB® workspace:

% clear % uncomment this line to clear the variables