Counterpart to `Hash#key?` for `Array`
key? to tell if a key exists without checking the value. It would be convenient if there were a counterpart in
Array. Suppose it is called
Array#index?. Then it should behave as follows:
[1, 2, 3].index?(2) # => true [1, 2, 3].index?(3) # => false [1, 2, 3].index?(-3) # => true [1, 2, 3].index?(-4) # => false
This is useful when we want to insert/move/delete elements to/from a certain position of an array. Without checking if a value exists, it can be messed up. Implementing a check is cumbersome now. With the proposed method, it would become easy.