This is a quickie: we just have an array like this

(alpha,beta,gamma)

and we want it reversed:

(gamma,beta,alpha)

Here is the code in bash:

a=(alpha beta gamma delta epsilon);
len=${#a[@]};

echo ${a[@]};

i=0;
while (($i < $len/2 )); do
     tmp=${a[i]};
     a[i]=${a[$len-$i-1]};
     a[$len-$i-1]=$tmp;  
     ((i++));
done

echo ${a[@]};