怎么优化嵌套循环次数不定的代码

echo trac_rows=${trac_rows}
count=0;
# start to dispose the options
if [ ${trac_rows} -eq 1 ]; then
{
    LOOP=$((${start[1]}))
    while [[ $LOOP -le $((${end[1]})) ]]; do
    {
        echo LOOP[1]=$LOOP
        echo count=$count
        count=$((count+1))
        LOOP=`expr ${LOOP} + $((${step[1]}))` 
    }
    done
}
elif [ ${trac_rows} -eq 2 ]; then
{
    LOOP[1]=$((${start[1]}))
    while [[ ${LOOP[1]} -le $((${end[1]})) ]]; do
    {
        LOOP[2]=$((${start[2]}))
        while [[ ${LOOP[2]} -le $((${end[2]})) ]]; do
        {
            echo LOOP[2]=$LOOP
            echo count=$count
            count=$((count+1))
            LOOP[2]=`expr ${LOOP[2]} + $((${step[2]}))`
        }
        done
        LOOP[1]=`expr ${LOOP[1]} + $((${step[1]}))` 
    }
    done
}
else
{
    echo "too many nesting options"
}
fi