C++ Constants

Service definitions may include constants and/or enums. The constants may be numbers, numeric arrays, or strings. Constants may exist at the service definition scope, within objects, or within structures. See Constants for more information. Enums exist as the service definition level. See Enums for more information.

An example of a service definition containing constants and enums:

service example.constants_example1

constant uint32 myconst 0xFB
constant double[] myarray {10.3, 584.9, 594}
constant string mystring "Hello world!"

enum myenum
    value1 = -1,
    value2 = 0xF1,
    value3,
    value4
end

The RobotRaconteurGen Utility is used to generate thunk source for the service definition, using the utility directly, or using the CMake macro. See CMake and Robot Raconteur Thunk Source Generation for more information. The thunk source places constants in a special constants namespace for the service definition. This namespace is within the namespace of the service definition, and has the fully qualified name with dots replaced with two underscores, with Constants prefixed. For instance, the service definition above with name experimental.constants_example1 will place the constants in the namespace example::constants_example1::example__constants_example1Constants. Enums are placed in a namespace to prevent values from leaking into the service definition namespace.

The above example will generate the following code in the thunk source:

namespace example
{
namespace constants_example1
{

namespace example__constants_example1Constants
{
    static const uint32_t myconst=0xFB;
    static const double myarray[]={10.3, 584.9, 594};
    static const char* mystring="Hello world!";
}

namespace myenum
{
enum myenum
{
    value1 = -1,
    value2 = 0xf1,
    value3 = 0xf2,
    value4 = 0xf3
};
}

}
}