Thank you for your help again.

C  (C :=abs~( ar[y]-~ec );) is really useful, Thank you! 

Another problem:

In practical problem, r is a large table, r[i] i=1..80

so I want to use for loop to storge results.

If r[i] is a list, must I program as follow?

r1 := [ op(r1), x ]

r2 := [ op(r2), x ]

.

.

r80 := [ op(r80), x ]

Thank you!

Thank you for your help again.

C  (C :=abs~( ar[y]-~ec );) is really useful, Thank you! 

Another problem:

In practical problem, r is a large table, r[i] i=1..80

so I want to use for loop to storge results.

If r[i] is a list, must I program as follow?

r1 := [ op(r1), x ]

r2 := [ op(r2), x ]

.

.

r80 := [ op(r80), x ]

Thank you!

Thank you for your help. The solution is good. I use it in another question and it works well.

Thank you!

Thank you for your help. The solution is good. I use it in another question and it works well.

Thank you!

Thank you for your help, it's a common way to solve the complex question!

Thank you for your help, it's a common way to solve the complex question!

Thank you for your help! I tried it, but it doesn't work.
If I change  r[]:=[]:  to r:=[]:

there is an error:Error, invalid subscript selector

I don't know the reason, Would you help me again?

Thank you for your help! I tried it, but it doesn't work.
If I change  r[]:=[]:  to r:=[]:

there is an error:Error, invalid subscript selector

I don't know the reason, Would you help me again?