abcgarden's profile - activity

I know the answer to the first one now. The value of ${prefix} is the path where package.xml locates.

I have several questions related to this topic:

1. What is the value of ${prefix} in package.xml? Is it an env variable?

2. How can I output these values?

3. Are there any other "hidden" variables like this one in package.xml?

4. Is it possible to run system command in package.xml, such as $(rospack find std_msgs) ?

5. Is it a general question applicable to all xml files or is it only ROS-specific?

Thanks.

Thank you @dan, @Thomas. Actually, these two answers combine to be the best answer. But in the std_msgs/Float64 there is one filed "float64 data". It seems that the initial float64 is defined elsewhere. What's the source?

Many ROS message uses the date type float64 so I decided to use this type in my code but I have this error:

   error: ‘float64’ does not name a type
             private: float64 direction_x_;
                      ^

I cannot find out the definition of float64. Anyone can tell me what files I should include to find out this data type definition?

It seems that there is no migration guide for Groovy? @BennyRe

Does it mean that I have to re-write a new code using Moveit! or I can use the Moveit! substitute header files(messages)?

Do you mean the "regression_test_pose_goal_floorobj.cpp"? No, I don't create it; it comes with the groovy distro. @BennyRe

I have asked a specific question last time, now I want to ask a more general question to which the answer will be definitely helpful to people who also have the confuse like I do. The question is:

There are always many changes to files(the content and the file name!) from one ROS version to another version. So I want to know what kind of changes have been made(as detailed as possible) so that I can modify my program to run in the new ROS version. I think my possible solution is either one of the following:

Condition I: what is no longer available in the new ROS version is a header file 
Solution: Copy-paste the old header file into the package folder of the new ROS version and include it in the source code.

But the problem is the header file maybe rely on other header files so I will copy-paste many of them.

Consition II: what is no longer available in the new ROS version is a package
Solution: 1. Copy-paste the whole package to the package directory of the new ROS version and  "depend" on it.
2. Find out similar package in the new ROS version and change my programs.

Solution 1 is direct but seems not practical, the old package may not be compatible with new ROS and another problem is how to make it "dependable"?

Solution 2 seems better but it involves much work to do. The most important thing is how to find out a similar package? Should I compare each class, function and variable between them(I have to compare each new package?!) And in each package there are many classes, functions and it takes me much time to understand them. And even worse, if there is no similar package, I should write a new package available in the new ROS.

Any suggestion or more possibly better solutions to my question?

I am using ROS groovy on Ubuntu precise. Recently I am trying to convert a code which works on Diamondback to Groovy. But the problem is that some files used to be available in Diamondback now does not exist in Groovy. For example, when I look at file "regression_test_pose_goal_floorobj.cpp" located at "/opt/ros/groovy/stacks/arm_navigation/move_arm/test/regression_test_pose_goal_floorobj.cpp ", it has "#include <arm_control_msgs/TrajectoryStart.h>" but I cannot find TrajectoryStart.h, even worse, I cannot find out any folder or file named arm_control_msgs in the root directory of groovy. When I search for the dos of packages of Diamondback and Electric, I cannot find out anything similar to arm_control_msgs. So :

1. anyone can help me find out where "arm_control_msgs" is?
2. Or tell me what kind of changes have been made to this file(or package?) in Groovy so that I cannot include the new version of header file in my program or make some changes to my program.

Thank you. I think you are right. But my question goes furthur, in a general case,(not necessarily ROS), how to find out the meaning for ${}. gvdhoorn gives one possible answer.

Where Does "catkin_make", "rosmake" and "make" Look to Find its Header Files? (In my question, "make" represents "catkin_make", "rosmake" and "make" :) ) Because of the update of ROS versions, some header files which work in older version do not exist in new version of ROS, which turns out to be a "cannot find xxx header file" error when "make"-ING. What I am going to do is to find out those old header files I need and copy to the path where "make" search for those header files(Is it an advisable behavior?).