c++ out of range at memory location error - c++

Question

Here is the code I have for a programing assignment I have. Im getting this error when I run the program
"Unhandled exception at at 0x772BC41F in STRUCT2.EXE: Microsoft C++ exception: std::out_of_range at memory location 0x0043ED04." If I understand this right, the error means my array has exceeded the allotted memory space. is that correct? and if this is correct, what am I doing wrong? My input file has less than 30 elements in it.
#include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cmath>
#include <sstream>
#include <cctype>
using namespace std;
struct Element
{
string Name;
char eN1;
char eN2;
float Weight;
};
struct Formula
{
char Element1;
char ElementA;
int Atom;
};
void ELEMENTS(Element ElmAry[30]);
float Str2Float(string Weight);
void FORMULAS(Formula FormAry[30]);
float CalculateMoleculeWeight(Element ElmAry[30], Formula FormAry[30]);
int main()
{
ifstream inputFile1;
ifstream inputFile2;
ofstream outputFile;
inputFile1.open("Element.txt");
inputFile2.open("Formula.txt");
outputFile.open("Molecular Weight.txt");
Element ElmAry[30];
Formula FormAry[30];
char inputCh;
int i = 0;
string String1;
string mFor;
string ABRV;
int ElmDigit = 0;
float StringWeight = 0;
string Name;
string Weight;
int LENGTH = 0;
float MOLEWT;
if(!inputFile1)
{
cout << "Couldn't find the Element.txt file." << endl;
return 0;
}
if(!inputFile2)
{
cout << "Couldn't find the Formula.txt file." << endl;
return 0;
}
ELEMENTS(ElmAry);
while(inputFile1)
{
Name = String1.substr(0,2);
ElmAry[i].Name = Name;
Weight = String1.substr(3,10);
String1.clear();
StringWeight = Str2Float(Weight);
ElmAry[i].Weight = StringWeight;
i++;
}
i--;
FORMULAS(FormAry);
while (inputFile2)
{
getline(inputFile2,String1);
LENGTH = String1.length();
int j = 0;
int n = 0;
while( j < LENGTH)
{
int pos = 0;
pos = String1.find(')');
while(n < LENGTH)
{
inputCh = String1.at(n);
if(isalpha(inputCh) && isupper(inputCh))
{
FormAry[j].Element1 = String1.at(n);
n++;
inputCh = String1.at(n);
}
if(isalpha(inputCh) && islower(inputCh))
{
FormAry[j].ElementA = String1.at(n);
n++;
inputCh = String1.at(n);
}
if(ispunct(inputCh))
{
n++;
inputCh = String1.at(n);
ElmDigit = (inputCh-'0');
}
if(isdigit(inputCh))
{
FormAry[j].Atom = ElmDigit;
n++;
}
inputCh = String1.at(n);
j++;
if(iscntrl(inputCh))
{
n++;
inputCh = String1.at(n);
j++;
}
n++;
}
}
}
MOLEWT = CalculateMoleculeWeight(ElmAry, FormAry);
cout << "\t\t MOLECULAR WEIGHT CHART \t\t\n" << endl;
cout << "\n| FORMULA |\t " << "\t| ATOM.WT |" << endl;
cout << "_______________________________";
outputFile << "\t\t MOLECULAR WEIGHT CHART \t\t\n" << endl;
outputFile << "\n| FORMULA |\t " << "\t| ATOM.WT |" << endl;
outputFile << "_______________________________";
for (int a = 0; a < 30; a++)
{
cout << MOLEWT << endl;
outputFile << MOLEWT << endl;
}
inputFile1.close();
inputFile2.close();
outputFile.close();
cin.get();
cin.get();
return 0;
}
void ELEMENTS(Element ElmAry[30])
{
for(int i = 0; i < 30; i++)
{
ElmAry[i].Weight = 0;
}
}
void FORMULAS(Formula FormAry[30])
{
for(int x = 0; x < 30; x++)
{
for(int x = 0; x < 9; x++)
{
FormAry[x].Atom = 1;
}
}
}
float Str2Float (string x)
{
stringstream ss(x);
float StringWeight;
ss >> StringWeight;
return StringWeight;
}
float CalculateMoleculeWeight(Element ElmAry[30], Formula FormAry[30])
{
int i;
int j=0;
float MoleWT = 0;
float MoleSum = 0;
char e1;
char e2;
char f1;
char f2;
for(i = 0; i < 30; i++)
{
f1 = FormAry[j].Element1;
f2 = FormAry[j].ElementA;
e1 = ElmAry[i].eN1;
e2 = ElmAry[i].eN1;
if
(e1 == f1 && e2 == f2)
{
MoleWT = ElmAry[i].Weight * FormAry[j].Atom;
MoleSum = MoleSum + MoleWT;
j++;
}
}
return MoleSum;
}
when I get to
while(inputFile1)
{
Name = String1.substr(0,2);
ElmAry[i].Name = Name;
Weight = String1.substr(3,10);//invalid string position
String1.clear();
StringWeight = Str2Float(Weight);
ElmAry[i].Weight = StringWeight;
i++;
}
i--;
Weight = String1.substr(3,10); gives me an invalid string position

Answer 1

std::out_of_range is an exception you get when you attempt to access memory outside the space you've allocated (in an STL container). In this particular case, you are accessing areas of a std::string that has not been allocated:
Weight = String1.substr(3,10); // empty string or string.length() < 4 throws here
std::string::substr takes index parameters that must be within the bounds of the array encapsulated by std::string. If the string is only 2 characters long, and you attempt to get characters starting at the 4th position, you will see the std::out_of_range exception. You should check the length prior to doing this kind of operation.
Additionally, you are declaring your arrays:
Element ElmAry[30];
Formula FormAry[30];
But you are looping through an entire file (which potentially has more than 30 elements). Thus, when i >= 30, you are out of bounds (and behavior will be undefined).
You can fix that by using std::vector, which will allow the array to be dynamically sized, or another collection (e.g. std::list, std::deque).