int registerDisk(lua_State* luaSt)
{
    return registerStruct(luaSt,
                          DISK_TYPE,
                          gettersDisk,
                          settersDisk,
                          metaMethodsDisk,
                          methodsDisk);
}
int registerNBodyCtx(lua_State* luaSt)
{
    return registerStruct(luaSt,
                          NBODYCTX_TYPE,
                          gettersNBodyCtx,
                          settersNBodyCtx,
                          metaMethodsNBodyCtx,
                          methodsNBodyCtx);
}
int registerSpherical(lua_State* luaSt)
{
    return registerStruct(luaSt,
                          SPHERICAL_TYPE,
                          gettersSpherical,
                          settersSpherical,
                          metaMethodsSpherical,
                          methodsSpherical);
}