Hi Morgan,
Okay -- say I wanted to read in just the range values from sicklms -- how can I just grab those? When I use rostopic echo /scan, the ranges show up as a list within brackets - is there a way I can pick out data from a topic my node is subscribing to? Sorry if I'm being a bit dense -- I'm not well versed on handling data types in C++.
Best,
Rishi

Rishi Bedi
rbedi100@gmail.com


On Thu, Jul 15, 2010 at 3:00 PM, Morgan Quigley <mquigley@cs.stanford.edu> wrote:
Hi Rishi,

Since there are such a wide variety of data types in the system that
would need different useful string representations, the auto-generated
message types don't create a string-generation function. You'll need
to assemble a string yourself using stringstream or whatever.

Cheers,
Morgan


On Thu, Jul 15, 2010 at 11:55 AM, Rishi Bedi <rbedi100@gmail.com> wrote:
> Hi,
> I'm trying to write a node that subscribes to the "/scan" topic, which is
> published by sicktoolbox_wrapper. I tried to modify some of the code given
> in the "Writing a Simple Publisher/Subscriber" tutorial:
>
> #include <ros/ros.h>
> #include <std_msgs/String.h>
> #include <sensor_msgs/LaserScan.h>
>
> void scanCallback (const sensor_msgs::LaserScan::ConstPtr& scan_msg)
>
> {
>   ROS_INFO("Received [%s]", scan_msg);
> }
>
> int main(int argc, char** argv)
> {
>   ros::init(argc, argv, "listener");
>   ros::NodeHandle n;
>   ros::Subscriber scan_sub = n.subscribe("scan", 100, scanCallback);
>   ros::spin();
> }
>
> The part where I think I'm getting tripped up is line 8 (the ROS_INFO
> command) -- how do I handle the unique data type LaserScan that
> sicktoolbox_wrapper uses to publish the scan data? I want to print the range
> values out, preferably as one long string -- what is the best way to convert
> the LaserScan type data into a string (or array)?
>
> Thanks a lot --
> Rishi
>
> Rishi Bedi
> rbedi100@gmail.com
>
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>
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