@gal

I have put restart in a separate execution group and remove iter:=iter+1 from the loop. It does not help. This time Maple writes : Error, invalid loop. I'm unable understand why it is invalid. Why you can't reproduce this example?

@Carl Love  This is an example:

restart:  eps:=1e-12; itermax:=10;  Error:=10;   for iter from 0 while Error>eps   and  iter<itermax  do;
                 print("iteration", iter, "Error", Error); Error:=Error*0.1;  iter:=iter+1;         end do;