Beyond the C++ Standard Library: An Introduction to Boost [Electronic resources] نسخه متنی

How Does the Conversion Library Improve Your Programs?

Understandable, maintainable, and consistent polymorphic conversions

Static downcasting using safer constructs than static_cast

Range-preserving numeric conversions that ensure correct value logic and less time debugging

Correct and reusable lexical conversions that lead to less time coding

The versatility of C++ is one of the primary reasons for its success, but sometimes also a formidable source of headaches because of the complexity of certain parts of the language. For instance, the rules for numeric conversions and type promotions are far from trivial. Other conversions are trivial, but tedious; how many times do we need to write a safe function[1] for converting between strings and ints, doubles and strings, and so on? Conversions can be problematic in every library and program you write, and that's how and why the Conversion library can help. It provides facilities that prevent dangerous conversions and simplify recurring conversion tasks.

[1] To avoid using sprintf and its ilk.

The Conversion library consists of four cast functions that provide better type safety (polymorphic_cast), better efficiency with preserved type safety (polymorphic_downcast), range-checked numeric conversions (numeric_cast), and lexical conversions (lexical_cast). These cast-like functions share the semantics of the C++ cast operators. Like the C++ cast operators, these functions have an important quality that, together with type safety, sets them apart from C-style casts: They unambiguously state the programmer's intent.[2] The importance of the code we write goes far further than its implementation and present behavior. More important is to clearly convey our intents when writing it. This library makes it somewhat easier by extending our C++ vocabulary.

[2] They can also be overloaded, which sometimes makes them superior to the C++ cast operators.