Abstract. The iterator abstraction is one of the most commonly used in
programming, but implementing an iterator type can be challenging. The
requirements for a standard-conforming iterator are at once tedious and
subtle: tedious because much of an iterator’s rich interface is “boilerplate”
surrounding a few core operations, and subtle because of the intricate
details involved in getting that interface right. This paper presents
the generalized iterator template from the Boost Iterator Adaptor Library.
In addition to automating the error-prone and redundant job of implementing
new iterator types, the library simplifies the creation of iterator
types that are variations on other iterators (adapted iterators) and generators
of new iterator families (iterator adaptors). The Iterator Adaptor
Library is an example of policy-based design and employs template
meta-programming. We also present the Policy Adapter implementation
pattern, a strategy which can also be used to generate new representatives
of other abstract concept families.
