Chapter 3. Manipulating Structured Data IN THIS CHAPTER All parts should go together without forcing. You must remember that the parts you are reassembling were disassembled by you. Therefore, if you can't get them together again, there must be a reason. By all means, do not use a hammer. IBM maintenance manual (1925) Simple variables are not adequate for real-life programming. Every modern language supports more complex forms of structured data and also provides mechanisms for creating new abstract data types. Historically, arrays are the earliest known and most widespread of the complex data structures. Long ago, in FORTRAN, they were called subscripted variables. Today they have changed somewhat, but the basic idea is the same in all languages. More recently, the hash has become an extremely popular programming tool. Like an array, a hash is an indexed collection of data items; unlike an array, it may be indexed by any arbitrary object. (In Ruby, as in most languages, array elements are accessed by a numerical index.) Finally, in this chapter we will look at more advanced data structures. Some of these are just special "views" of an array or hash; for example, stacks and queues can be implemented easily using arrays. Other structures such as trees and graphs may be implemented in different ways according to the situation and the programmer's preference. But let's not get ahead of ourselves. We will begin with arrays. | 
