Chapter 22. Boost.Ratio 1.0.1

Howard Hinnant

Beman Dawes

Vicente J. Botet Escriba

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Overview

Motivation
Description

How to Use This Documentation

This documentation makes use of the following naming and formatting conventions.

Code is in fixed width font and is syntax-highlighted.
Replaceable text that you will need to supply is in italics.
Free functions are rendered in the code font followed by (), as in free_function().
If a name refers to a class template, it is specified like this: class_template<>; that is, it is in code font and its name is followed by <> to indicate that it is a class template.
If a name refers to a function-like macro, it is specified like this: MACRO(); that is, it is uppercase in code font and its name is followed by () to indicate that it is a function-like macro. Object-like macros appear without the trailing ().
Names that refer to concepts in the generic programming sense are specified in CamelCase.

	Note
	In addition, notes such as this one specify non-essential information that provides additional background or rationale.

Finally, you can mentally add the following to any code fragments in this document:

// Include all of Ratio files
#include <boost/ratio.hpp>
using namespace boost;

Boost.Ratio aims to implement the compile time ratio facility in C++0x, as proposed in N2661 - A Foundation to Sleep On. That document provides background and motivation for key design decisions and is the source of a good deal of information in this documentation.

Description

The Boost.Ratio library provides:

A class template, ratio, for specifying compile time rational constants such as 1/3 of a nanosecond or the number of inches per meter. ratio represents a compile time ratio of compile time constants with support for compile time arithmetic with overflow and division by zero protection.
It provides a textual representation of boost::ratio<N, D> in the form of a std::basic_string which can be useful for I/O.
Some extension related to the Rational Constant concept enabling the use of ratio<> in the context of Boost.MPL numeric metafunctions.