@Kitonum 
Thanks, it works!

@tomleslie Wow, thank you so much! Your code is so much simpler.

@Carl Love Thank you so much, now I understand the problem.

Sorry for the stupid question.

@acer 
Sorry, I haven't properly typed the whole text of my program.
n is given a value before.
In fact, this procedure works perfectly except for the weird problem with array and exprseq.

(I'll correct the initial post, thank you)