From: Pavel Vozenilek (pavel_vozenilek_at_[hidden])
Date: 2003-04-27 15:03:43
"Terje Slettebø" <tslettebo_at_[hidden]> wrote in message
>From: "Pavel Vozenilek" <pavel_vozenilek_at_[hidden]>
>> Currency conversion as drop-in library is IMHO not possible - currencies
>> differ from strict units like weight and future applications may require
>> functionality beyond current requirements.
> Well, your library is very general, where you provide conversion functions
> between any two types. If you define each currency as a type, wouldn't
> cover the functionality for converting between currencies? If not, what
> could be needed?
OK, I mean it would be very hard to create library which already provides
conversion routines. quantity.hpp is only kit to use the user provided
conversion routines easier.
> I realise that in this case, it may be a lot of functions to define, to
> define the conversion between any two currencies - for e.g. 20 currencies,
> that's around 400 functions to define.
Not for quantity.hpp. One unit (quantity) there is primary ('privileged')
and conversions are possible between this and other units. Then it is
possible to do secondary unit 1 -> primary unit -> secondary unit2
conversion. This is model of many real systems.
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