一个计算数字数组概览的算法

已知数组 a = [0,1,2,3,5,7,8,9]
要求输入其“概览” [0..3,5,7..9]

用ruby实现如下：

def sum_ary(ary)
    tmp = []
    start_v,end_v=-1,-1
    is_start = false
    idx = 0
    count = ary.count
    ary.each_with_index do |v,i|
        if(i+1<count)
            sub = ary[i+1] - v
            if(sub == 1)
                if(is_start)
                    next
                else
                    is_start = true
                    start_v = v
                end
            else
                if(is_start)
                    is_start = false
                    end_v = v
                    tmp.push(Range.new(start_v,end_v))
                else
                    tmp.push(v)
                end
            end
        else
        #condition for i+1>=count
            if(is_start)
                is_start = false
                end_v = v
                tmp.push(Range.new(start_v,end_v))
            else
                tmp.push(v)
            end
        end
    end
    tmp
end