Problem with how to assign an array

[Steven W. Orr]

I know how to assign a simple array. My problem is a bit harder.

I have three arrays

a1=(aaa bbb ccc ddd)
a2=(qqq www eee rrr)
a3=(fff ggg hhh)

I then set a_all

a_all=("${a1[*]}" "${a2[*]}" "${a3[*]}"

Later on, I decide which element of a_all I really want. So with my new index 
calculated, I say

real_a=( ${a_all[index]} )

And it worked really well until today. The problem is that I need an element 
of the aNs to be allowed to be null values.

Like this:

a1=(aaa bbb ccc ddd '' jjj kkk lll)

such that if index is 0, I'd like real_a to end up with 8 elements instead of 7.

I could create a sentinel, I could use a case statement, I could create all 
kinds of confabulations, but I'd like to know if there's a better way to do it.

I literally tried everything I could think of.

Thanks :-(

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