Elementary Data Structures

This chapter is an introduction to the construction of data structures in Ada using arrays, records and access types. Here we discuss the language support for implementing data structures; their encapsulation into abstract data types will be presented in the next chapter.

The case study is the implementation of a priority queue, first using arrays and then using pointers. A priority queue is a data structure that stores items so that retrieval of the item of the highest priority can be done efficiently, although insertion of new items may be less efficient. In the case study, we assume that the items are simply integers and that higher-priority items have lower values. This is a common situation: customers in a store take numbered tickets and the lowest outstanding number is served first.