Write a ros node in c++ called followplan that works as follows. The node subscr

Question

Write a ros node in c++ called followplan that works as follows.  The node subscribes to a topic called commands that delivers messages of type std_msgs::Char (characters) and publishes to the topic turtle1/cmd_vel, i.e., velocity commands. The node is both a publisher and a subscriber. If the node receives the character 'F' (forward) it moves the turtle forward 1m. If it receives the character 'B' (back) it moves the turtle back one meter. If it receives the character 'R' (right) it turns clockwise 90 degrees, whereas if it receives the character 'L' (left) it turns counterclockwise 90 degrees.

Explanation / Answer

//EXAMPLE PROGRAM FOR SINGLE LINKED LIST
# include <iostream.h>
# include <conio.h>
# include <stdlib.h>
struct node
{
int number;
node *next;
};
class singlelist
{
node *first,*prev,*temp,*curr;
public:
singlelist()
{
first=NULL;
}
void create()
{
cout<<"Stop by -999"<<endl;
temp=new node;
cout<<"Enter the numbers ";
cin>>temp->number;
while(temp->number!=-999)
{
   temp->next=NULL;
   if(first==NULL)
   {
   first=temp;
   prev=first;
   }
   else
   {
   prev->next=temp;
   prev=temp;
   }
temp=new node;
cin>>temp->number;
} //end of while
}

void deletenode()
{
int num;
cout<<" Enter the number to delete ";
cin>>num;
if(first->number==num)
{
first=first->next;
return;
}
else
{
prev=first;
curr=first->next;
while(curr->next!=NULL)
{
if(curr->number==num)
{
prev->next=curr->next;
return;
}
prev=curr;
curr=curr->next;
}
}
if(curr->number==num)
{
prev->next=NULL;
return;
}
cout<<" No such number";
}

void insertbefore()
{
int nu;
temp=new node;
cout<<" Enter the number ";
cin>>temp->number;
cout<<" before the number ";
cin>>nu;
temp->next=NULL;
prev=first;
curr=first;
/* if(first==NULL) //if the list is empty then we can insert in this way
{
first=temp;
return;
}*/
if(curr->number==nu)
{
temp->next=first;
first=temp;
return;
}
else
{
prev=curr;
curr=curr->next;
while(curr->next!=NULL)
{
if(curr->number==nu)
{
prev->next=temp;
temp->next=curr;
return;
}
prev=curr;
curr=curr->next;
}
}
if(curr->number==nu)
{
prev->next=temp;
temp->next=curr;
return;
}
cout<<" No such number ";
}

void insertafter()
{
int nu;
temp=new node;
cout<<" Enter the number ";
cin>>temp->number;
cout<<" After the number ";
cin>>nu;
temp->next=NULL;
prev=first;
curr=first;
/* if(first==NULL) //if the list is empty then we can insert in this way
{
first=temp;
return;
}*/
if(curr->number==nu)
{
temp->next=first->next;
first->next=temp;
return;
}
else
{
prev=curr;
curr=curr->next;
while(curr->next!=NULL)
{
if(curr->number==nu)
{
temp->next=curr->next;
curr->next=temp;
return;
}
prev=curr;
curr=curr->next;
}
}
if(curr->number==nu)
{
curr->next=temp;
temp->next=NULL;
return;
}
cout<<" No such number ";
}

void print()
{
cout<<" The list is "<<endl;
cout<<" ----------- "<<endl;
temp=first;
while(temp!=NULL)
{
cout<<temp->number<<"-->";
temp=temp->next;
}
cout<<"Nil"<<endl;
getch();
}
};

void main()
{
int ch=0;
singlelist s;
clrscr();
cout<<" Linked List creation ";
s.create();
clrscr();
while(ch!=5)
{
clrscr();
cout<<" 1.Insert Before";
cout<<" 2.Insert After";
cout<<" 3.Delete ";
cout<<" 4.Print ";
cout<<" 5.Exit ";
cout<<" Enter your choice ";
cin>>ch;
switch(ch)
{
   case 1:
       s.insertbefore();
       s.print();
       break;
   case 2:
       s.insertafter();
       s.print();
       break;
   case 3:
       s.deletenode();
       s.print();
       break;
   case 4:
       s.print();
       break;
   case 5:
       s.print();
       exit(1);
}
}
getch();
}

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