for s in selection do print classOf s as string

Because print can have only one argument. :)

Kostadin explain why.
And if you want advanced debagging fn (with more arguments input) you can use *format* fn. I suppose you already know that. :)

You need to add brackets like this

for s in selection do print (classOf s as string)
--or this is my sugesstion
for s in selection do print (getClassName s)

thanks for help (again)
but I have some problems with max. When you make too much errors in listener,
after a while nothing works,... I need to reboot max...

Sometimes if you forget to close brucket of your code max will not print the result.
Try to ** interrupted ** max with Escape key.
If you this not help then you have srious problem. Reset max as usual

:)