5.6 Performing Currency Exchanges in C++

The following C++ code shows how exchange rates and tables, exchange objects and groups, and the exchange factory come together to perform a currency exchange. The comments in the code detail each part of the program.
#include <rw/money/money.h>
#include <rw/money/euroexchggrp.h>
#include <rw/money/divexchggrp.h>
#include <rw/money/exchgfact.h>
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// Create and initialize an exchange rate table
// to be used for all currency conversions.   
RWExchangeRateTable rateTable;
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// Create an exchange factory that uses the exchange rate
// table created above.  By default the exchange factory contains
// the multiplication exchange group.   
RWExchangeFactory<double> exchangeFactory( rateTable );

// Add a Euro exchange group
ifstream euroCurrenciesFile( "euro_currencies.in" );
RWExchangeGroup<double> euroGroup = 
                RWEuroGroup<double>::create( euroCurrenciesFile );
exchangeFactory.appendExchangeGroup( euroGroup );

// Add a division exchange group
RWExchangeGroup<double> divGroup =
                         RWDivisionGroup<double>::create();
exchangeFactory.appendExchangeGroup( divGroup );

// The exchange factory contains three exchange groups:
// an RWMultiplicationGroup, an RWEuroGroup, and an
// RWDivisionGroup, in that order. 

// Get an exchange object from the factory for converting Belgian
// Francs to Canadian Dollars. Since the factory's exchange rate 
// table contains a conversion factor for converting Belgian Francs
// to Canadian Dollars, it creates an exchange object containing
// an RWMultiplicationExchange implementation. Exchanges will be 
// computed by multiplying the source amount by the conversion 
// conversion factor.
RWExchange<double> befToCadExchanger = 
                   exchangeFactory.getExchange( "BEF", "CAD" );

// Get an exchange object from the factory for converting Belgian
// Francs to French Francs.  The factory's exchange rate table does
// not contain a conversion factor for converting Belgian Francs to
// French Francs.  Belgium and France are members of the EMU, so
// instead, the exchange rate table contains conversion factors for
// converting Euros to Belgian Francs and Euros to French Francs. 
// This means that the Factory creates an RWExchange object with an
// RWTriangularExchange implementation.
RWExchange<double> befToFrfExchanger =
                   exchangeFactory.getExchange( "BEF", "FRF" );

// Get an exchange object from the factory for converting Belgian
// Francs to Euros.  The factory's exchange rate table does not
// contain a conversion factor for converting Belgian Francs to
// Euros and the Euro is not a local Euro currency.  There is,
// however, a conversion factor for converting Euros to Belgian
// Francs in the factory's exchange rate table. Thus the last 
// exchange group in the list, RWDivisionGroup, creates an exchange 
// object with an RWDivisionExchange implementation.
RWExchange<double> befToEURExchanger = 
                   exchangeFactory.getExchange( "BEF", "EUR" );

// Do the exchanges, using the exchange function of each exchange 
// object.
RWMoney<double> moneyBEF( 189972.76, "BEF" );
if ( befToCadExchanger.isValid() )
{
  RWMoney<double> moneyCAD = befToCadExchanger.exchange(moneyBEF);
}

if ( befToFrfExchanger.isValid() )
{
  RWMoney<double> moneyFRF = befToFrfExchanger.exchange(moneyBEF);
}

if ( befToEURExchanger.isValid() )
{
  RWMoney<double> moneyEUR = befToEURExchanger.exchange(moneyBEF);
}