AMDG Zachary Turner wrote:
On Thu, Jul 2, 2009 at 2:07 PM, Steven Watanabe<watanabesj@gmail.com> wrote:
AMDG
Zachary Turner wrote:
Thanks for your help so far! I know I'm probably just making this too difficult, but it's still not working. I guess I should just post a complete sample so that we can eliminate the snip factor from the list of possible causes (I put them in the boost namespace for the sake of consistency but the same problem arises regardless).
<snip> void foo() { using boost::units::quantity; using namespace boost::units::data_capacity;
//Both of these fail with the message that there is no conversion to the destination //type because the construcor is explicit quantity<data_capacity> compressed_size = 1000 * bytes; quantity<data_capacity, int> compressed_size2 = 1000 * bytes;
Implicit conversion between different units is not allowed. Try quantity<data_capacity> compressed_size(1000 * bytes);
Thanks. The confusion came from the fact that the syntax I was trying was being used in some of the examples. But there is something different about those examples, so that's why it wasn't working. One of the trig examples has a line:
quantity<plane_angle> theta = 0.375*radians;
for example. I suppose it's due to the fact that radians are the "primary" unit for this dimension?
The difference is that plane_angle is the same unit as radians. In your case, data_capacity is defined as bits, while you are assigning it a value in bytes. Since the units change, the conversion is explicit.
That aside, I still think something isn't exactly right. Ultimately I need to be able to print these quantities in different units (for example, if I'm transferring data at 100MB/s I don't want to print this in bits / second). All of these seems to only allow printing of a quantity in its base unit, which here is defined to be bits. I'd like to be able to do something like:
quantity<capacity> q = 2180321.0 * bytes; std::cout << q * megabytes << std::endl;
The units of q are bits. Thus, the units of the expression that you are printing are bits * megabytes which is printed as "b MB"
It seems like this should "just work" since I've defined them all as scaled based units, but instead the first example just prints
1.74426e+007 b MB
which means all its doing is formatting it as bits and then appending "MB"
In Christ, Steven Watanabe