Thread: got a problem in ltoa ()

hello, i have a problem in converting an octal number to its binary form, using ltoa...
well i have a small program in C , that does this job , just fine ,
but i have to make it in C++, meaning i will not need any scanf() , so here is the problem , i dont know how i can feed the ltoa ! if i convert a decimal number to octal (suppose i is the decimal number , i convert it to octal and save it again in 'i' , when i use it in ltoa, it wont work!!)
(see the following example, it just works fine, but if i omit scanf("%o",&i) , and i feed the ltoa (the number 77 which is octal )it wont work! if i use a decimal number and convert it to octal and then feed the ltoa , again it wont work!! where is the problem ? is there any counterpart for C++? or a way to manipulate octals ? i mean we have "%0" in C , do we have such thing is C++ that returns an octal number?

Code:

/* ltoa example */
#include <cstdio>
#include <cstdlib>

int main ()
{
  int i,k;
  char buffer [sizeof(long)*8+1];
  char * str;
  printf ("Enter a number: ");
  scanf ("%o",&i);
  ltoa (i,buffer,10);
  printf ("decimal: %s\n",buffer);
  ltoa (i,buffer,16);
  printf ("hexadecimal: %s\n",buffer);
  ltoa (i,buffer,2);
  printf ("binary: %s\n",buffer);
  system("pause");
  return 0;
}

The global main function returns an int, and ltoa is non-standard. Unfortunately, there is no direct standard library replacement for ltoa, except for the special cases of octal, decimal and hexadecimal. As a basic example:

Code:

#include <iostream>

int main()
{
    int num;
    std::cout << "Enter a number in octal: ";
    std::cin >> std::oct >> num;

    std::cout << "decimal: " << std::dec << num << std::endl;
    std::cout << "hexadecimal: " << std::hex << num << std::endl;
}

You could use a stringstream to actually save the converted result to a string instead of printing it immediately.

Originally Posted by laserlight

The global main function returns an int, and ltoa is non-standard. Unfortunately, there is no direct standard library replacement for ltoa, except for the special cases of octal, decimal and hexadecimal. As a basic example:

Code:

#include <iostream>

int main()
{
    int num;
    std::cout << "Enter a number in octal: ";
    std::cin >> std::oct >> num;

    std::cout << "decimal: " << std::dec << num << std::endl;
    std::cout << "hexadecimal: " << std::hex << num << std::endl;
}

You could use a stringstream to actually save the converted result to a string instead of printing it immediately.

would you explain more ? i have no clue what a string stream is !( havent read about that yet!

Originally Posted by Masterx

would you explain more ? i have no clue what a string stream is !( havent read about that yet!

Read about that part then
You could search the Web if necessary.

tanx ok.im on it

i couldnt manage to figure stringstream stuff out ! so i made my own Octal to Binary convertor
please check this out and tell me if anything is wrong. many tanx in advance :

Code:

int Oct2Bin(int n)
{
         int a[6],i=0,t=0;
         string str,b;
         while(n!=0)
         {
                 a[i]=n%10;
                 n=n/10;
                 if(a[i]>7)
                 t=1;
                 i++;
         }
         i--;
         if(t==0)
          for(;i>=0;i--)
          {
                  switch(a[i])
                   {
                           case 0:
                           if (!str.empty())
                           str.append("000");
                           else
                           str="000";
                           break;

                           case 1:
                           if (!str.empty())
                           str.append("001");
                           else
                           str="001";
                           break;

                           case 2:
                           if (!str.empty())
                           str.append("010");
                           else
                           str="010";
                           break;

                           case 3:
                           if (!str.empty())
                           str.append("011");
                           else
                           str="011";
                           break;

                           case 4:
                           if (!str.empty())
                           str.append("100");
                           else
                           str="100";
                           break;

                           case 5:
                           if (!str.empty())
                           str.append("101");
                           else
                           str="101";
                           break;

                           case 6:
                           if (!str.empty())
                           str.append("110");
                           else
                           str="110";
                           break;

                           case 7:
                           if (!str.empty())
                           str.append("111");
                           else
                           str="111";
                           break;
                   }
          }
         cout<<str;

         if(t==1)
          {
                
                 return -1;
return 0;          }
}

What, exactly, about stringstreams did you fail to understand?

Originally Posted by Elysia

What, exactly, about stringstreams did you fail to understand?

tanx for your attention dear Elysia, well cause i was kinda in hurry i just googled the string stream and a bunch of links appeared! glancing at the examples , i couldnt find it out! anyway ,(i will go for it next time , ) would you now tell me why this program fails! (im sure thats because of loop where Memory[5][i] gets stuffed! )

Code:

#include <cstdlib>
#include <iostream>
#include <cstdio>
#include <string>
using namespace std;

string ob(int);


int main(int argc, char *argv[])
{
    int b,i=0;
    char memory[5][10];
    string str;
    cout<<"enter a number ";
    cin>>b;
    str = ob(b);
    if (str =="no")
    {
            cout<<"your number is not octal!!";
    }
    else 
    {
        for (int i=0;i<9;i++)
         {
               memory[5][i]=str[i];
         
         }
         
     }
     //cout<<memory[5][i];
   // cout<<ob();
    system("PAUSE");
    return EXIT_SUCCESS;
}
string ob(int n)
{
         int a[6],i=0,t=0,it;
         string str,b,str1,str2,not_octal;
         
         
         while(n!=0)
         {
          a[i]=n%10;
          n=n/10;
          if(a[i]>7)
           t=1;
          i++;
         }
         i--;
         if(t==0)
          for(;i>=0;i--)
          {
           switch(a[i])
           {
            case 0:
             if (!str.empty())
              str.append("000");                   
             else str="000";
             break;
             
            case 1:
            if (!str.empty())
            str.append("001");
            else str="001";
            break;
            
            case 2:
             if (!str.empty())
            str.append("010");else
             str="010";
             break;
            
            case 3:
             if (!str.empty())
            str.append("011");else
             str="011";
             break;
            
            case 4:
            if (!str.empty())
           str.append("100");else
            str="100";
             break;
            
            case 5:
             if (!str.empty())
             str.append("101");else
             str="101";
             break;
            
            case 6:
             if (!str.empty())
            str.append("110");else
             str="110";
             break;
            
            case 7:
             if (!str.empty())
            str.append("111");else
             str="111";
             break;
           }
          }
          str1="000000";
          str2="000";
              if (str.length()==3)
              {
                                  str1.append(str);
                                  str=str1;
              }
                                  
              if (str.length()==6)
              {
                                  str2.append(str);
                                  str=str2;     
              }            
              
              cout<<str;
         
         if(t==1)
          {
                 not_octal="no";
                 //printf("Not an Octal number\n");
                 return not_octal;
return str;          }
}

Code:

    int num;
    std::cout << "Enter a number in octal: ";
    std::cin >> std::oct >> num;

    std::stringstream stream;
    stream << num;
    std::cout << stream.str().c_str();

Example: http://www.cppreference.com/wiki/io/...m/constructors

As for your code, element 5 does not exist. 0-4 does.
Furthermore, you MUST improve your indentation.
And avoid working with legacy char.
If you work with arrays, use std::tr1::array or boost::array.

Originally Posted by Masterx

Code:

{
         int a[6],i=0,t=0;
         string str,b;
         while(n!=0)
         {
                 a[i]=n%10;
                 n=n/10;
                 if(a[i]>7)
                 t=1;
                 i++;
         }
         i--;
         if(t==0)
          for(;i>=0;i--)
          {
                  switch(a[i])
                   {
                           case 0:
                           if (!str.empty())
                           str.append("000");
                           else
                           str="000";
                           break;

                           case 1:
                           if (!str.empty())
                           str.append("001");
                           else
                           str="001";
                           break;

                           case 2:
                           if (!str.empty())
                           str.append("010");
                           else
                           str="010";
                           break;

                           case 3:
                           if (!str.empty())
                           str.append("011");
                           else
                           str="011";
                           break;

                           case 4:
                           if (!str.empty())
                           str.append("100");
                           else
                           str="100";
                           break;

                           case 5:
                           if (!str.empty())
                           str.append("101");
                           else
                           str="101";
                           break;

                           case 6:
                           if (!str.empty())
                           str.append("110");
                           else
                           str="110";
                           break;

                           case 7:
                           if (!str.empty())
                           str.append("111");
                           else
                           str="111";
                           break;
                   }
          }
         cout<<str;

         if(t==1)
          {
                
                 return -1;
return 0;          }
}

Originally Posted by Elysia

Code:

    int num;
    std::cout << "Enter a number in octal: ";
    std::cin >> std::oct >> num;

    std::stringstream stream;
    stream << num;
    std::cout << stream.str().c_str();

Example: http://www.cppreference.com/wiki/io/...m/constructors

As for your code, element 5 does not exist. 0-4 does.
Furthermore, you MUST improve your indentation.
And avoid working with legacy char.
If you work with arrays, use std::tr1::array or boost::array.

mant tanx dear Elysia . my bad ( i completely forgot that!!tanx again )
about indentation , is the above post indented properly?
and about boost arrays ! is it not necessary to install boost library before using them? or are they just ordinary header files?! (include them and use em!)

Refer to http://cpwiki.sourceforge.net/Indentation for indentation advice and how it's done properly.
Boost::array exists in a header, so you only need the header and no compiling & installing. Unless your compiler supports TR1, in which case you should be able to find it in std::tr1::array in a header called "array" I believe (or some such).

by the way , that didnt help either! you know the program compiles fine , it ouputs the binary form , there a " Windows dont send error window " appears !! and it crashes!!

Code:

#include <cstdlib>
#include <iostream>
#include <cstdio>
#include <string>
using namespace std;

string Oct2Bin(int);


int main(int argc, char *argv[])
{
        int b,i=0;
        char memory[5][10];
        string str;
    
        cout<<"enter a number ";
        cin>>b;
    
        str = Oct2Bin(b);
        if (str =="no")
        {
                cout<<"your number is not octal!!";
        }
        else 
        {
            for (int i=0;i<9;i++)
             {
                   memory[4][i]=str[i];
         
             }
         
         }
     //cout<<memory[5][i];
   // cout<<ob();
        system("PAUSE");
        return EXIT_SUCCESS;
//in the name of God
//Octal To Binary Convertor
//Protype : string Oct2Bin( int );
}

string Oct2Bin(int n)
{
         int a[6],i=0,t=0;
         string str,str1,str2,not_octal;
         while(n!=0)
         {
                 a[i]=n%10;
                 n=n/10;
                 if(a[i]>7)
                 t=1;
                 i++;
         }
         i--;
         if(t==0)
          for(;i>=0;i--)
          {
                  switch(a[i])
                   {
                           case 0:
                           if (!str.empty())
                           str.append("000");
                           else
                           str="000";
                           break;

                           case 1:
                           if (!str.empty())
                           str.append("001");
                           else
                           str="001";
                           break;

                           case 2:
                           if (!str.empty())
                           str.append("010");
                           else
                           str="010";
                           break;

                           case 3:
                           if (!str.empty())
                           str.append("011");
                           else
                           str="011";
                           break;

                           case 4:
                           if (!str.empty())
                           str.append("100");
                           else
                           str="100";
                           break;

                           case 5:
                           if (!str.empty())
                           str.append("101");
                           else
                           str="101";
                           break;

                           case 6:
                           if (!str.empty())
                           str.append("110");
                           else
                           str="110";
                           break;

                           case 7:
                           if (!str.empty())
                           str.append("111");
                           else
                           str="111";
                           break;
                   }
          }
          str1="000000";
          str2="000";
              if (str.length()==3)
              {
                        str1.append(str);
                        str=str1;
              }

              if (str.length()==6)
              {
                        str2.append(str);
                        str=str2;
              }

         cout<<str;

         if(t==1)
          {
                  not_octal="no";
                 //cout<<"Not a Octal number\n";
                 return not_octal;
return str;          }
}

Code:

#include <iostream>
#include <string>
#include <sstream>

int main()
{
	int Num;
	std::cout << "Enter a number: ";
	std::cin >> std::oct >> Num;
	
	std::stringstream sstr;
	sstr << Num;
	std::cout << sstr.str().c_str() << std::endl;
}

Although, don't ask me why the output is incorrect; I'm not much into this kind of thing.

well, so how should i know what is wrong with it! im really confused!

Why not have Oct2Bin take a string as its argument? If you really want it to take an int as an argument then you are merely expressing the number in binary as opposed to converting it from an octal representation to a binary representation.