Weird error

[BenjaminB]

Hi!

As you will soon note, I am such a noob to this C++ thing...
I am creating (or at least trying) a calculator that allows you to make operation with mathematic vectors, as a way of getting some practice. I have recently come up with this error message when debuging: "An Access voilation was raised in your program". When running the program without debuging the error messaje displayed is the following: "The instruction in 0x0004015a6 refers to the memory in 0xfffffffe. The memory could not be written." (As I roughly translate from Spanish). The complier Im using is wxDev-C++.
Here I paste the code of the program, which is quite short and has explaining comments:

wxwidgets:

#include <cstdlib> 
#include <iostream> 

using namespace std; 

int main(int argc, char *argv[]) 
{ 
    char p[10]; 
    cout<<"Vectors Calculator"<<endl<<endl;         //introduction to the 
    cout<<"Developed by X"<<endl;    //program 
    GOBACK: 
    cout<<"Do you wish to start? (y/n)"<<endl;      //dumb question 
    cin>>p; 

    while ((*p!='y' && *p!='n')||p[1]!=00){         //will print "ERROR" 
        cout<<"ERROR"<<endl;                        //if you type any weird 
        cin>>p;                                     //stuff different from 'y' 
    }                                               //or "n". 
    if (*p=='y') 
        cout<<"Introduce the dimension of the vectors"<<endl; //Further instructions 
    else if (*p=='n'){ 
        char ex [10];                                      //Will let you leave the program 
        cout<<"Enter 'e' to exit"<<endl;                   //if you are not ready to start... 
        cin>>ex;                                           //bleh... 
        if (*ex=='e'){ 
            return EXIT_SUCCESS; 
            } 
        else if (*ex!='e'||ex[1]!=00){       //If you dont want to leave... 
            goto GOBACK; 
            } 
        } 
    int R;                                  //R woudl be the "dimension" 
    cin>>R;                                 //which you will now enter. 
    long double **vectorStore;              //Creates a matrix where vectors you 
    for(int i=0;i<100;i++){                 //introduce will be stored. 
        vectorStore[i]= new long double [R];//<------------------- 
    }                                                          //This loop creates 
    cout<<"Now enter the vectors elements one by one"<<endl;   // 100 vectors of the decired size. 
    cout<<"Vectors will be printed for control."<<endl; 
    for (int i=0; i<100; i++){       //This loop lets you introduce 
        vectorStore [i];             //vecotors elements. 
        for (int j=0; j<R; j++){ 
            cin>>vectorStore [i] [j];  
        }                              
        cout<<"V"<<(i+1)<<"=[ "; 
        for (int j=0; j<R; j++){                //This loop prints each vector 
            cout<<vectorStore [i] [j]<<" ";     //you introduce. 
        } 
        cout<<"]"<<endl; 
        cout<<"Do you wish to introduce another vector?(y/n)"<<endl; 
        char p[10]; 
        cin>>p; 
        while ((*p!='y' && *p!='n')||p[1]!=00){ //Same as the first "while"  
        cout<<"ERROR"<<endl;                    //but for the vector adding. 
        cin>>p;    
        } 
        if (*p=='y'){                    //Go on with the loop... 
            cout<<"Continue..."<<endl; 
        } 
        else if (*p=='n'){ 
            break;                      //Break the loop... 
        } 
    } 
    cout<<"Now you can:"<<endl; 
    cout<<"-Print all vectors.(p)"<<endl; 
    cout<<"-Operation with vectors.(o)"<<endl;   //More work needs to be done. 
system ("PAUSE"); 
    return 0; 
}

When I choose to break into the process (while debuging), it takes me to this line:
vectorStore[i]= new long double [R];//<-------------------
Which leaves me clueless, because I had been running this exact code, added some stuff, got the error for the first time, then went back to the good version and now I cant get this error off no matter what I do.

Thank you very much,
Benjamin.

[Albatross]

Segmentation faults are lots of fun.

That said, why aren't you using actual vectors?
vector<vector<long double> > vectorStore;
http://cplusplus.com/reference/stl/vector/

-Albatross

[BenjaminB]

Thanks for the quick reply Albatross,

I havent used actual vector because my level of noobness doesnt allow it. Ill explain: I have roughly read a basic tutorial, one like the one this site provides. My intention is to keep reading, but I just wanted to give it a try, when I came up to this... a real P.I.A. I believe that using actual vectors may be more convenient, but am I doing something wrong here? or is just the complier and/or windows vista feels like making me misserable?

Again, thanks.
Benjamin.

[firedraco]

Your issue is that you are trying to access the ith element of your vectorStore, but you haven't initialized the first row yet. You need something like:

vectorStore = new long double*[100];

Although I would really suggest you use vectors instead so you don't have to deal with memory management.

[Albatross]

EDIT: firedraco beat me to the error.

After you get around all the template nonsense, vectors are actually quite easy to use. Here...

vector<type> naem; //Declaring a vector.
//You can use vectors as type, but be sure to include a space to differentiate <vector<type> > and <vector<type>>.
naem.at(location); //Getting stuff from a vector.
//Where location is an address just like the one you would use in an array.
naem.push_back(new_stuff); //Appending stuff to a vector.
//Where new_stuff has type... type. 

-Albatross

[BenjaminB]

Well... It worked!!

Thank you!

I inserted that line between lines 34 and 35 of the first code and it worked as spected.
Now I will do as suggested and keep reading.

Benjamin.

EDIT: Albatross, thanks for the extra explanation. You can consider this threat solved.

thank you both guys.