Ben Strasser wrote:
Jeff Garland <jeff <at> crystalclearsoftware.com> writes:
typedef unit<length, "m"> meter; This isn't valid code...can't give char strings to templates. I was talking about an ideal world. ;)
Ok, well we don't have that world...
The problem is hardcoding the "m" anywhere -- this shouldn't be done. You need an I/O facet that has the defaults and can be overridden by the user at runtime. This allows different output for the same value in the same process. Your view of how to solve this is on the wrong course in my view...
I depends on the situation. Some units are unique to the application. Here we probably wont need any internationalization so hard coding "m" will do the job just fine.
Boost is an international organization with an international audience so it's a different context to do something only for yourself.
There are however also other units. For example length units. It might be useful to let the programmer use meters in his program and have it output feet based on the local in the stream.
What I mean is something like:
cout.imbue(new unit_out_facet<length, feet>("", "ft")); wcout.imbue(new unit_wout_facet<length, feet>(L"", L"ft")); //or cout.imbue(new unit_out_facet<length, meter>("", "m")); wcout.imbue(new unit_wout_facet<length, meter>(L"", L"m")); //... cout<<meter(4); // will print meter or feet based on the current local
This seems as a good idea to me and this is possbile to implement.
On the right track, but this scares me a bit. I'm not sure I want conversions in the facet code. I think I'd rather the user do that explicitly.
Input would be a bit more tricky.
Input is much harder...because you only have access to an input iterator. You can't backtrack. So suppose you want to handle input like this: 10 m 10 meters 10 microseconds The first 2 are a valid length -- the last isn't. Anyway, it's sticky.
Don't take this as criticism -- I suppose I could have taken this on by now given my experience. I'm just hoping someone will take up my challenge No, I don't. I like hearing other peoples opinions.
Good :-) Jeff