Hello, I have 1 error but I don't know what is it??

[nano90]

Write ONE C++ program that displays a menu with 4 choices and executes those choices for the end-user.
Your menu should include an informative header/description at the top of the Windows 32 console followed by the following menu text (written in bold here):
Choose one of the following, or choose to quit this program.

1. Display ASCII characters with codes from 32 to 256
2. Show two patterns using the '+' character
3. Read random numbers from a file and perform calculations on them
4. Quit

_________

#include<iostream>
#include<fstream>
#include<iomanip>
#include<cmath>


using namespace std;

int main()
{
 int option = 0;

 while (option!=4)
 {
 cout << endl;
 cout<<"choose one of the following options." << endl;
 cout<<"1. Print out ASCII characters." << endl;
 cout<<"2. Print out patterns." << endl;
 cout<<"3. Read random.txt." << endl;
 cout<<"4. Quit." << endl;
 cin >> option;
 if (option==1)
 {
 for(int i=1; i<=255-32; i++)
   {
    cout << (char)(i+32) << " " ;
 if ((i % 16) == 0)
     {
     cout << endl;
     }
   }
 }
 else if (option==2)
 {
 for(int i=0; i<10; i++)
 {
 for(int j=0; j<=i; j++)
 {
 cout << "+";
 }
 cout << endl;
 }
  for(int i=10; i>0; i--)
 {
  for(int j=0; j<i; j++)
  {
  cout << "+";
  }
  cout << endl;
  }
 }
 else if (option==3)
 {
 int total = 0;
 int size = 0;
 ifstream ifs( "E:\\random.txt" );
 string s;

 while( getline( ifs, s ) )
 {
 if ( s.length()>0 )
  {
  int v = atoi(s.c_str());
  size++;
  total = total + v;
  }
 }
 cout << "file has " << size << " numbers" << endl;
 cout << "the total is " << total << endl;
 cout << "the average is " << (total/size) << endl;
 }
 else if (option==4)
   {
   cout<<"quit the program"<<endl;
   }
 }
 return 0;
}

[Albatross]

Your code compiles just fine, and it works perfectly UNTIL you get to option 3. If the file doesn't exist, the program will throw EXC_ARITHMETIC (divide by zero causes this).

And you don't want to use string::c_str() as an input to atoi(). Try searching for digits?
http://cplusplus.com/reference/string/string/find/

-Albatross

[rajroshi]

Hi nano,
I am a beginner, so don't know how fine is my solution. But let me try. When I checked the code it seems like when it was not getting any input from random.txt, it was giving error because behavior of division by 0 is undefined in c++ and that is what code is trying to do.

I modified code a bit by throwing domain_error exception and it is working fine.

Here is the modified code.

#include<iostream>
#include<fstream>
#include<iomanip>
#include<cmath>
#include<stdexcept>


using namespace std;

int main()
{
 int option = 0;

 while (option!=4)
 {
 cout << endl;
 cout<<"choose one of the following options." << endl;
 cout<<"1. Print out ASCII characters." << endl;
 cout<<"2. Print out patterns." << endl;
 cout<<"3. Read random.txt." << endl;
 cout<<"4. Quit." << endl;
 cin >> option;
 if (option==1)
 {
 for(int i=1; i<=255-32; i++)
   {
    cout << (char)(i+32) << " " ;
 if ((i % 16) == 0)
     {
     cout << endl;
     }
   }
 }
 else if (option==2)
 {
 for(int i=0; i<10; i++)
 {
 for(int j=0; j<=i; j++)
 {
 cout << "+";
 }
 cout << endl;
 }
  for(int i=10; i>0; i--)
 {
  for(int j=0; j<i; j++)
  {
  cout << "+";
  }
  cout << endl;
  }
 }
 else if (option==3)
 {
 int total = 0;
 int size = 0;
 ifstream ifs( "E:\\random.txt" );
 string s;

 while( getline( ifs, s ) )
 {
 if ( s.length()>0 )
  {
  int v = atoi(s.c_str());
  size++;
  total = total + v;
  }
 }
 try {
          if ( s.length()==0 )
  throw domain_error ("no valid input to read in random.txt");
  cout << "file has " << size << " numbers" << endl;
 cout << "the total is " << total << endl;
 cout << "the average is " << (total/size) << endl;

  }catch (domain_error err)
  {
      cout <<err.what();
        }


 }
 else if (option==4)
   {
   cout<<"quit the program"<<endl;
   }
 }
 return 0;
}

Hope it will work.

Regards

[Albatross]

Um... we absolutely HATE giving out full or even partial code solutions on this forum. Don't do it if you want to keep your fingers. ;)

Oh, and by the way, that solution is way overblown.
http://cplusplus.com/reference/iostream/ifstream/is_open/

-Albatross

[rajroshi]

@Albatross
Sorry man, I am new to c++ don't have very good knowledge as I have already described. Just trying to solve with my tiny knowledge.

And code I am just copy pasting, no hard work. But I will keep in account your advice

Thanx