PNP variables

In PNP, there is the possibility to write parametric plans (i.e., plans that contain variables).

Variables are represented with a string starting with the @ character, they are reset at the beginning of each execution (init place), can get values during plan execution, and use the values later on in the plan.

For example, it is possible to define an action GoTo_@X_@Y_@Theta where the three variables @X, @Y, and @Theta are instantiated at plan execution time, before execution of the action.

There are several ways to instantiate PNP global variables:

1. send an event of the form GoTo_instance1_instance2_instance3, it will instantiate the variables with the instances provided (in this case X=instance1, Y=instance2, Theta=instance3).

Example: use topic /pnp/conditionEvent of type String

rostopic pub /pnp/conditionEvent ...  'setvar_@X_instance1'

2. use the ROS service pnp/setVariableValue of type PNPSetVariableValue

     string variable
     string value
     ---
   

Example: rossrv call pnp/setVariableValue ...

3. execute the action setvar_<var>_<value> in the plan

Example: setvar_@X_instance1

After instantiation, the global variables can be used in the plan (for example in execution nodes, such as in a node called GoTo_@X_@[email protected]).

To modify the values of the variables, just re-instantiate them as previously explained.

ROS Service pnp/getVariableValue of type PNPGetVariableValue

string variable
---
string answer

can be used to read the value of a PNP global variable