I need to retrieve the position of each lora node while adding the following code under SimpleLoRaApp::handleMessage :
cModule *host = getContainingNode(this);
IMobility *mobility = check_and_cast<IMobility *>(host->getSubmodule("mobility"));
Coord coord = mobility->getCurrentPosition();
ofstream outfile;
outfile.open("/home/user/Desktop/test.txt", std::ios_base::app); // append instead of overwrite
outfile << coord.x<<"\n";
outfile.close();
I get the positions of all nodes in the text file, but I can't retrieve the node index corresponding to each position. How do I retrieve the node ind
Related
2->7->8->11
|
13->16->17->21
|
22->23->27->29
|
30->32
Sorted Linked List given like above where each node has 2 pointers next and down. For each row starting nodes down points to next row start. Each row has 4 elements, except last one which can have <= 4 elements. Next rows start element is greater than previous rows end element. We need to design and code for it insert of new value at correct place and delete operation. I could not solve this problem.
Structure representation and Pseudo code for the add operation is as follows
And we can implement the delete recursively using the add data as example
typedef struct sibling{
int data;
struct sibling *nxt;
} t_sibling
typedef struct children {
struct sibling *sibling;
struct children *nxt;
} t_children;
add_element(t_children **head, int newdata)
{
t_children *walk_down = *head;
t_children *parent = NULL;
while (walk_down != NULL) {
if(parent == NULL && Compare newdata < head of current walk_down->sibling) {
// Code comes here when we add 1 to above mentioned list example
newdata is added to begining to head of walk_down->sibling
sibling_list_count++;
if (sibling_list_count > 4) {
taildata = delete_end from tail of walk_down->sibling
add_element(&walk_down, taildata)
}
break;
}
else if(newdata < head of current walk_down->sibling) {
if (Compare newdata > tail of parent sibling) {
// Code comes here when we add 12 to above mentioned list
newdata is added to begining to head of walk_down->sibling
if (sibling_list_count > 4) {
taildata = delete_end from tail of walk_down->sibling
add_element(&walk_down, taildata)
}
}
else {
// Code comes here when we add 6 to above mentioned list
newdata is added to the appropriate location of parent of sibling
Since above step disturbs the <= 4 property we
taildata = delete_end from tail of parent->sibling
add_element(&walk_down, taildata)
}
break;
}
parent = walk_down;
walk_down = walk_down->nxt;
}
}
I know how to calculate the total number of connected components in Boost, but is there an efficient way to compute the size of the largest connected component using the boost's graph library.
I think the most efficient way is to replace the component map with a custom type.
I created a small WritePropertyMap to do that:
template <typename V>
struct Mapper {
using Id = int; // component id
using Cardinality = int;
using Map = boost::container::flat_map<Id, Cardinality>;
using Value = Map::value_type;
Map& storage;
friend void put(Mapper& m, V const& /*v*/, Id id) { m.storage[id] += 1; }
Value largest() const {
return not storage.empty()
? *max_element(begin(storage), end(storage),
[](Value const& a, Value const& b) {
return a.second < b.second;
})
: Value{};
}
};
We need to tell Boost about our property map:
template <typename V> struct boost::property_traits<Mapper<V>> {
using category = boost::writable_property_map_tag;
using key_type = V;
using value_type = int;
};
Note
The separation between storage and property map is because property maps are passed by value - and should be cheap to copy.
Now we can use it, adapting the library example slightly:
Live On Coliru
Mapper<V>::Map result;
Mapper<V> mapper{result};
int num = connected_components(g, mapper);
auto [id, cardinality] = mapper.largest();
std::cout << "Largest component #" << id << " (out of " << num
<< " components) has " << cardinality << " vertices\n";
Prints
Largest component #0 (out of 3 components) has 3 vertices
This matches the expected output.
BONUS
If you have an expected number of components, you may be able to optimize storage by using small_vector/static_vector, e.g.
using Value = std::pair<Id, Cardinality>;
using Map = boost::container::flat_map<
Id, Cardinality, std::less<>,
boost::container::small_vector<Value, 10>>;
This way, unless you have more than 10 components, you will never see a dynamic allocation for the mapper storage.
i have two vectors. one is a (1) vector which contains all objects im using and works with that. the other vector is a (2) vector which after a function adds an object from (1) into (2). once this happens i want to remove the object from (1). the problem is that the function i made to remove it takes in a object * obj. the actual object still has pointers pointing to it and i dont want to fully wipe the obj, just remove it from (1). any help would be appreciated.
`
void removeObject(const Object * obj) {
int index;
for (int i = 0; i < size(); i++) {
if (obj == & objectVector[i] ) {
index = i;
}
}
objectVector.erase(objectVector.begin() + index);
}
`
im sure this is the problem because when i dont comment out the line using this function i get a sigtrap error
I am writing an simple parser&rewriter tools for PL/SQL, and I've complete the parser and get the AST,but now I got two problems :
How can I get certain nodes of the AST ,so as to change the value of them?
After change the nodes ,how can i regenerate the SQL from the updated AST
does the ANTLR AST provide similar interface to do this?
Example SQL: select a,b from t where a=2
After parser the sql and get the ast, I want to change the sql into
select fun(a),b from t where a = fun1(2);
BTW, I generate the AST for C with ANTLR,
Thank you for any suggestion!
See my SO answer on how to regenerate source code from an AST.
Its a lot more work than you think.
ANTLR provides some help in the form of string templates but you may find these a mixed blessing: while they can generate code text, they will generate precisely what is in the template, and you may want to regenerate the code according to its original layout,
which the layout of the string template wants to override.
The following code will walk the AST and print all AST nodes to stderr.
The same tree walker is the basis for a tree transformer that can replace tree nodes.
Allocate new tree nodes with: (pANTLR3_BASE_TREE)(psr->adaptor->nilNode(psr->adaptor));
Delete AST nodes with: parentASTnode->deleteChild(parentASTnode, nodeIndex);
[deleteChild does not free the deleted nodes]
Replace nodes with: parentASTnode->replaceChildren(parentASTnode, nStartChildIndex, nStopChildIndex, newASTnode);
[you cannot insert nodes in the middle of an AST tree level, you can only replace nodes or add to the end of the parent nodes child list]
void printTree(pANTLR3_BASE_TREE t, int indent)
{
pANTLR3_BASE_TREE child = NULL;
int children = 0;
char * tokenText = NULL;
string ind = "";
int i = 0;
if ( t != NULL )
{
children = t->getChildCount(t);
for ( i = 0; i < indent; i++ )
ind += " ";
for ( i = 0; i < children; i++ )
{
child = (pANTLR3_BASE_TREE)(t->getChild(t, i));
tokenText = (char *)child->toString(child)->chars;
fprintf(stderr, "%s%s\n", ind.c_str(), tokenText);
if (tokenText == "<EOF>")
break;
printTree(child, indent+1);
}
}
}
// Run the parser
pANTLR3_BASE_TREE langAST = (psr->start_rule(psr)).tree;
// Print the AST
printTree(langAST, 0);
// Get the Parser Errors
int nErrors = psr->pParser->rec->state->errorCount;
I am trying to implement a simple singly linked list of integers which are to be sorted upon insertion in Visual Studio c++ 2010 express.
The problem is that when I create a new node and call the .getValue() function on it, the correct number is returned, however somehow that is being lost when I try calling getValue() on a node already in the list. The node might not be inserted into the list correctly, however I can't find why that would be the case. Some other value which looks like a reference value or something is displayed instead of the correct value.
I added current to the watch window when debugging but was still unable to see any of my variables other than the give value to be inserted. I am new to visual studio so I'm not sure if I'm missing something there. Here is my code:
#include "Node.h";
#include <iostream>
//namespace Linked{
//The first two constructors would be the first in the linked list.
Node::Node(void){
value = 0;
next = 0;
}
Node::Node(int setValue){
value = setValue;
next = 0;
}
Node::Node(int setValue,Node *nextNode){
value = setValue;
next = nextNode;
}
Node * Node::getNext(){
return next;
}
void Node::setNext(Node newNext){
next = &newNext;
}
int Node::getValue(){
return value;
}
bool Node::isEqual(Node check){
return value==check.getValue()&&next == check.getNext();
}
/*
int main(){
int firstInt, secondInt;
std::cin>>firstInt;
Node first = Node(firstInt);
std::cout<<"Enter second int: ";
std::cin>>secondInt;
Node second = Node(secondInt, &first);
std::cout<<"Second: "<<second.getValue()<<"\nFirst: "<<(*second.getNext()).getValue();
system("pause");
}*/
Here is the linked list:
//LinkedList.cpp
LinkedList::LinkedList(void)
{
head = 0;
size = 0;
}
LinkedList::LinkedList(int value)
{
head = &Node(value);
size = 1;
}
void LinkedList::insert(int value){
if(head == 0){
Node newNode = Node(value);
head = &newNode;
std::cout<<"Adding "<<(*head).getValue()<<" as head.\n";
}else{
std::cout<<"Adding ";
Node current = *head;
int numChecked = 0;
while(size<=numChecked && (((*current.getNext()).getValue())<value)){
current = (*(current.getNext()));
numChecked++;
}
if(current.isEqual(*head)&¤t.getValue()<value){
Node newNode = Node(value, ¤t);
std::cout<<newNode.getValue()<<" before the head: "<<current.getValue()<<"\n";
}else{
Node newNode = Node(value,current.getNext());
current.setNext(newNode);
std::cout<<newNode.getValue()<<" after "<<current.getValue()<<"\n";
}
}
size++;
}
void LinkedList::remove(int){
}
void LinkedList::print(){
Node current = *head;
std::cout<<current.getValue()<<" is the head";
int numPrinted = 0;
while(numPrinted<(size-1)){
std::cout<<(current.getValue())<<", ";
current = (*(current.getNext()));
numPrinted++;
}
}
int main(){
int a[5] = {30,20,25,13,2};
LinkedList myList = LinkedList();
int i;
for(i = 0 ; i<5 ; i++){
myList.insert(a[i]);
}
myList.print();
system("pause");
}
Any guidance would be greatly appreciated!
When you create nodes in insert, you're allocating them off the stack, which means that they'll be lost after the function returns.
Get them off the heap with:
Node * newNode=new Node(value);
When you use:
Node newNode=Node(value);
You're allocating that object on the stack, which means that pointers:
&newNode
to it are only valid until that function returns. If you use heap memory this is no longer an issue, but it does mean that you have to implement a destructor for your list which goes through and deletes each node.