Version 5.0 The LEDA User Manual

Chapter 13
Graphs and Iterators
13.1 Introduction
13.1.1 Iterators
Iterators are a powerful technique in object-oriented programming and one of the fundamental
design patterns [39]. Roughly speaking, an iterator is a small, light-weight object,
which is associated with a specific kind of linear sequence. An iterator can be used to
access all items in a linear sequence step-by-step. In this section, different iterator classes
are introduced for traversing the nodes and the edges of a graph, and for traversing all
ingoing and/or outgoing edges of a single node.
Iterators are an alternative to the iteration macros introduced in sect. 11.1.3.(i).
example, consider the following iteration pattern:
For
node v;
forall_nodes (n, G) { ... }
Using the class NodeIt introduced in sect. 13.2, this iteration can be re-written as follows:
for (NodeIt it (G); it.valid(); ++it) { ... }
The crucial differences are:
• Iterators provide an intuitive means of movement through the topology of a graph.
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