Not able to figure out why this code gives error.
#include<iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
unsigned long long A[102];
A[0]=2;
int main()
{
cout<<"OK";
}
Error while compiling:
prog.cpp:6:1: error: ‘A’ does not name a type
But this works fine.
#include<iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
unsigned long long A[102];
int main()
{
A[0]=2;
cout<<"OK";
}
What could be the reason ?
This
A[0]=2;
is not an initialization, it is an assignment to the first element of A. You cannot do that outside of a function.
This is initialization, and is legal:
#include<iostream>
unsigned long long A[102] = {2};
int main()
{
std::cout<<"OK\n";
}
It will set the first element to 2 and all the rest to 0.
Related
why am i geting runtime error in one
thats my question i am writing this simply because it is showing to lksdjflksjflkjsdflk
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
long int L;
long int l;
cin>>L;
cin>>l;
long int ans=L%l;
if(L>=l)
{
cout<<ans;
}
else
{
cout<<L;
}
return 0;
}
Unless you provide the inputs for L,l and runtime error description... It's ambiguous and we have to guess.. hope you are not passing 0 to 'l'..
I am trying to create a function that returns in main.cpp in the header and .cpp file and run it in the main function.
This process I do works on main.
#include <iostream>
#include <sstream>
#include "Cards.h"
using namespace std;
//this function returns array
int *function1(){
int a=12;
int b=13;
int c=14;
static int list[3]={a,b,c};
return list;
}
int main(int argc, const char * argv[]) {
int *list;
list=function1();
cout<<list[1]<<endl;
return 0;
}
However, I cannot do these in a header and a separate cpp file.
I have a Cards header
#ifndef Cards_H
#define Cards_H
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
class Cards{
public:
char suit; //A,H,D,C,S. A is empty card
int number; //00-13
int visibilty;//0 - 1. O invisible 1 is visible
int * function2();
};
#endif
This is the class cpp file
#include "Cards.h"
using namespace std;
//function
int Cards:: function2(){
int a=12;
int b=13;
int c=14;
int list[3]={a,b,c};
return list; // error code Cannot initialize return object of type 'int Cards::*' with an lvalue of type 'int [3]'
}
How do I fix this problem and run it in main?
As pointed out in the comments, there is already a SO thread
Return array in a function
which handles your issue.
If your really want to use C arrays then your program shall look like:
Cards_CStyle.h:
#ifndef Cards_CStyle_H
#define Cards_CStyle_H
using namespace std;
class Cards {
public:
int* function2(int arr[]);
};
#endif
Cards_CStyle.cpp:
#include "Cards_CStyle.h"
using namespace std;
//function
int* Cards::function2(int arr[]){
int a=12, b=13, c=14;
arr[0] = a;
arr[1] = b;
arr[2] = c;
return arr;
}
main_CStyle.cpp:
#include <iostream>
#include "Cards_CStyle.h"
using namespace std;
int main(int argc, const char * argv[]) {
int arr[3]; // Take care that all your functions use size <= 3
Cards cards;
int* list=cards.function2(arr);
cout<<list[1]<<endl;
return 0;
}
As recommended in the comments, you should use the containers of the STL, e.g. array for fixed length or vector for variable length. Assuming that fixed length of 3 will be fine for you, then your code would be looking like this:
Cards_STLStyle.h:
#ifndef Cards_STLStyle_H
#define Cards_STLStyle_H
#include<array>
using namespace std;
typedef array<int, 3> my_array;
class Cards {
public:
my_array function2();
};
#endif
Cards_STLStyle.cpp:
#include "Cards_STLStyle.h"
using namespace std;
//function
my_array Cards::function2(){
int a=12, b=13, c=14;
return my_array { a,b,c};
}
main_STLStyle.cpp:
#include <iostream>
#include <array>
#include "Cards_STLStyle.h"
using namespace std;
int main(int argc, const char * argv[]) {
Cards cards;
my_array list=cards.function2();
cout<<list[1]<<endl;
return 0;
}
Please find more information here:
array
I would like to implement a hash table example.
So for this aim, I have created one header, one hash.cpp and main.cpp files.
in my hash.cpp , I tried to run a dummy hash function which takes key value and turns into an index value. however, it throws an error(reference to 'hash' is ambiguous) whenever I try to create an object according to that hash class.
this is my main.cpp:
#include "hash.h"
#include <iostream>
#include <cstdlib>
#include <string>
#include <stdio.h>
using namespace std;
int main(int argc, const char * argv[]) {
hash hash_object;
int index;
index=hash_object.hash("patrickkluivert");
cout<<"index="<<index<<endl;
return 0;
}
this is my hash.cpp:
#include "hash.h"
#include <iostream>
#include <cstdlib>
#include <string>
#include <stdio.h>
using namespace std;
int hash(string key){
int hash=0;
int index;
index=key.length();
return index;
}
this is my hash.h
#include <stdio.h>
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
#ifndef __hashtable__hash__
#define __hashtable__hash__
class hash
{
public:
int Hash(string key);
};
#endif /* defined(__hashtable__hash__) */
Your hash class symbol is clashing with std::hash
A quick fix could be using a global namespace qualifier
int main(int argc, const char * argv[]) {
::hash hash_object;
but a better and recommended one would be to stop polluting your global namespace with
using namespace std;
and just using std::cout or std::endl when you need them.
You could also create your own namespace in case you're writing a library.
Besides, you have some capital letter typos here:
index = hash_object.hash("patrickkluivert");
^ I suppose you're referring to the Hash() function here
and here
int Hash(std::string key) {
^ this needs to be capital as well
int hash = 0;
in case you want to match your declaration and avoid cast/linking errors.
Your hash class is conflicting with std::hash. Stop using using namespace std; right now. If you want to make print statements shorter, try using std::cout; using std::endl;
I am novice in c++. I have made class named Cache and made an object L1Cache using the constructor. I am passing parameters to the constructor and printing calculated data correctly. But when I am calling a different function within the same class and same object, data that I generated in constructor gives garbage value. Here, I would like to mention that my all functions and variables are public.
My code looks something like this:
main.cc:
#include <stdio.h>
#include <fstream>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include "cache.h"
main()
{
unsigned long long Address= 5555555555;
unsigned long a=5,b=7;
Cache L1Cache(a, b);
L1Cache.Calculate( Address);
}
cache.cc:
#include <stdio.h>
#include <iostream>
#include <fstream>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include "cache.h"
using namespace std;
Cache::Cache(unsigned long c,unsigned long d)
{
e= c+d;
printf("Value Of e:%lu",e);
}
void Cache::Calculate(unsigned long long A)
{
printf("Value of e:%lu",e);
}
cache.h:
class Cache
{
public:
unsigned long e;
Cache(unsigned long c,unsigned long d)
void Calculate(unsigned long long A);
}
output:
Value of e: =12;
Value of e: = garbage
There's a semicolon missing in and after your class declaration. And main should be int. After fixing that the code runs. Have you actually run the code you think you ran?
I have a class called pos... I am trying to poll a method from this class. I used pthread_create(pthread_t thread, pos::Pirnt_data,this);
I get an error that pos is not declared in the scope... I included the h file of pos but I don't understand. I think I am using a wrong format can somebody help me
#include "position.h"
#include "pthread.h"
#include "pos.h"
void position::tick(schedflags_t flags)
{
if(pthread_create(&thread,NULL,pos::Print_data,this)!=0) {
stringstream bad;
bad << "OPIMex: Could not create listener thread: "
}
this class position has method tick that runs every 1 second with the data. I am trying to poll a method Print data from the class pos but it gave me that error any ideas why ?
this is class pos.h
#ifndef POS_H_
#define POS_H_
#include <math.h>
#include <iostream>
#include <fstream>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <gps.h>
#include <string.h>
#include <pthread.h>
#include <string>
#include <vector>
#include <strings.h>
#include <math.h>
using namespace std;
namespace herpderp {
namespace modules {
int UBX_step =0;
long data;
int UBX_class;
int UBX_id=0;
int UBX_payload_length_hi;
int UBX_payload_length_lo;
int UBX_payload_counter =0;
int ck_a;
int ck_b;
int GPS_timer;
int fd;
unsigned int UBX_buffer[35];
int payload_data;
long lat=0;
long lon=0;
long alt_MSL=0;
long iTOW=0;
long alt=0;
unsigned long LastMS;
int UBX_Read;
vector <float> v;
fstream myfile;
int Open_port(void);
int read_tofile();
long join_4_bytes( unsigned int Buffer[]);
void parse_ubx_gps(void);
void checksum(char ubx_data);
void Print_data();
int push_data_into_vector();
int decode_gps();
int Configure_gps();
int test();
int Close_NEMA();
int Open_UBX();
}
}
#endif //POS_H_
pthread_kill is not on pthread.. It is on signal.h
#include <signal.h>
1) you can provide some code snippet/additional information to help you better.
2) If you are getting linkage error, check if you have linked with -lpthread library.
Form the pos.h it seems that there is no class called pos and you just need to call the function name:
if(pthread_create(&thread,NULL,Print_data,this)!=0) {