c++ dynamic array Floating Point exception -

for homework had design arraylist in c++ using 1d arrays , pointers make array dynamic. have done ample testing , functions work correctly, when use main teacher has provided me floating point error. point of homework create class work teachers main without changing code in main

here main:

#include "arraylist.h" #include <iostream> using namespace std;  int main(int argc,char *argv[]) {     arraylist arr;      (int i=1;i<=50;i++)     {         arr.push_back(i);     }      cout << "should contain numbers 1..50, ";      cout << arr.tostring() << endl;      (int i=arr.size()-1;i>=1;i--)     {         arr.erase(arr[i]);     }         cout << "should contain 1, ";     cout << arr.tostring() << endl;      arr.erase(arr[0]);      (int i=1;i<=50;i++)     {         if (i<=2)             arr.push_back(i);         else         {             int j=1;             while ((j<arr.size()) && (i%arr[j]!=0))                 j++;              if (j==arr.size())             {                 arr.push_back(i);             }         }     }      cout << "prime numbers between 1 , 50 are: " << arr.tostring() << endl;  } 

here cpp:

#include<iostream> #include<string> #include<sstream> #include "arraylist.h"  using namespace std; void arraylist:: intialarr(int arr[]) {     for(int = 0; < length; i++)     {         arr[i] = 0;     } }  string arraylist:: tostring() {     std::ostringstream ss;     for(int = 0; < capacity; i++)     {         if(arr[i]>0 || arr[i] <0)         {             ss << arr[i] << " ";         }     }     return ss.str(); }  arraylist::arraylist() {     length = 1;     capacity=0;     arr = new int[length];     intialarr(arr); }  int& arraylist:: operator[] (unsigned int i) {     return arr[i]; }  void arraylist:: push_back(int m) {     if(capacity>=length)     {           int oldlength = length;         length = length*2;        int* curarr = new int[length];        intialarr(curarr);        (int = 0; < oldlength; i++)        {           curarr[i] = arr[i];        }        delete [] arr;        arr = curarr;     }      arr[capacity] = m;     capacity++; }      void arraylist:: erase(int m) {         if(capacity == length/2)         {                length = length/2;             int* curarr = new int[length];             intialarr(curarr);               (int = 0; i<capacity; i++)         {                 curarr[i] = arr[i];          }         delete [] arr;         arr = curarr;         }          for(int = 0; < capacity; i++)         {             if(arr[i]==m)             {                 for(int j = i; j<length; j++)                 {                     arr[j] = arr[j+1];                 }                 capacity--;                 break;             }     }     cout << "length = " << length << " capacity = " << capacity << " capacity/length = " << capacity*2 << endl; } 

from have read online floating point exceptions thrown when try divide 0 or infinate value arises dont understand how getting either of these issues arise.

my code through main number 1-50 added , deleted error once go setting array hold prime numbers (after arr.erase(arr[0]) in main)

i set couple of tags in main find number going while ((j<arr.size()) && (i%arr[j]!=0))and find numbers before crash

j = 1 , arr[j] = 2 = 5 , arr.size() = 4