libs/units/example/runtime_unit.cpp
// Boost.Units - A C++ library for zero-overhead dimensional analysis and
// unit/quantity manipulation and conversion
//
// Copyright (C) 2003-2008 Matthias Christian Schabel
// Copyright (C) 2008 Steven Watanabe
//
// 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)
#include <map>
#include <iostream>
#include <boost/lexical_cast.hpp>
#include <boost/units/quantity.hpp>
#include <boost/units/cmath.hpp>
#include <boost/units/systems/si/length.hpp>
#include <boost/units/base_units/imperial/foot.hpp>
//[runtime_unit_snippet_1
namespace {
using namespace boost::units;
using imperial::foot_base_unit;
std::map<std::string, quantity<si::length> > known_units;
}
quantity<si::length> calculate(const quantity<si::length>& t)
{
return(boost::units::hypot(t, 2.0 * si::meters));
}
int main()
{
known_units["meter"] = 1.0 * si::meters;
known_units["centimeter"] = .01 * si::meters;
known_units["foot"] =
conversion_factor(foot_base_unit::unit_type(), si::meter) * si::meter;
std::string output_type("meter");
std::string input;
while((std::cout << "> ") && (std::cin >> input))
{
if(!input.empty() && input[0] == '#')
{
std::getline(std::cin, input);
}
else if(input == "exit")
{
break;
}
else if(input == "help")
{
std::cout << "type \"exit\" to exit\n"
"type \"return 'unit'\" to set the return units\n"
"type \"'number' 'unit'\" to do a simple calculation"
<< std::endl;
}
else if(input == "return")
{
if(std::cin >> input)
{
if(known_units.find(input) != known_units.end())
{
output_type = input;
std::cout << "Done." << std::endl;
}
else
{
std::cout << "Unknown unit \"" << input << "\""
<< std::endl;
}
}
else
{
break;
}
}
else
{
try
{
double value = boost::lexical_cast<double>(input);
if(std::cin >> input)
{
if(known_units.find(input) != known_units.end())
{
std::cout << static_cast<double>(
calculate(value * known_units[input]) /
known_units[output_type])
<< ' ' << output_type << std::endl;
}
else
{
std::cout << "Unknown unit \"" << input << "\""
<< std::endl;
}
}
else
{
break;
}
}
catch(...)
{
std::cout << "Input error" << std::endl;
}
}
}
}
//]