select reject detect inject用法

irb(main):047:0> a

=> [16, 256, 1296, 4096]

irb(main):048:0> a.select{|n| n>16}

=> [256, 1296, 4096]

irb(main):049:0> a.reject{|n| n>16}

=> [16]

irb(main):051:0> a.detect{|n| n==16}

=> 16

irb(main):052:0> a.inject{|acc,b| acc+b}
=> 5664