Smalltalk and Object Orientation: an Introduction - Free

11. Further Collection Classes
11.1 Introduction
This chapter continues the discussion of the collection class hierarchy. It concentrates on the ordered
collections and builds on the previous chapter. Sections two, three an
d four present the
SortedCollection class, the List class and the Interval Class. The Array class,
Dictionary class and String class are presented in Sections five to seven. Section eight describes
how to iterate over collections while Section nine explai ns how to convert between collections. Figure
11.1 illustrates the relationships between some of the ordered collection classes.
Figure 11.1: Some of the ordered collection classes
11.2 SortedCollection
A SortedCollection is a collection class in which the order of the elements is determined by a
specified sorting criteria (for example x i
< x i+1
). This is specified by the sort block associated with every
sortedCollection object. That is, the ordering is defined by a special block of code (for example, [:x
:y | x>= y]). This block can be replaced by the user of the class so that any type of ordering can be
applied to the objects with in the collection. Why not browse the class using the class browser. Try and
find out what type of sorting algorithm is being used.
Try out the following in a Workspace:
| x |
x := SortedCollection new.
x add: 5.
x add: 6.
x add: 7.
x add: 1.
x inspect.
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