Goto Command

This is a discussion on Goto Command within the C++ Programming forums, part of the General Programming Boards category; I have heard that you can use the GOTO command in C++ as I did in BASIC. is this true, ...

  1. #1
    Its hard... But im here swgh's Avatar
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    Goto Command

    I have heard that you can use the GOTO command in C++ as I did in BASIC. is this true, and also, how do you use it? Do Ii have to declare the command at the start of the code in
    int main()?

    Any help would be appriciated

  2. #2
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    how do you use it?
    You don't. Period.

  3. #3
    Registered User major_small's Avatar
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    Quote Originally Posted by 7stud
    You don't. Period.
    agreed.

    but here: http://www.cppreference.com/keywords/goto.html

    again, DO NOT USE GOTO.
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  4. #4
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    technically you can use it
    http://www.sscnet.ucla.edu/geog/gessler/borland/cpp.htm

    Anyway.

    A related question since goto statements are a no no in c++, how do you exit a nested loop?

    I've got 4 nested for loops( actually i've only got 3 atm, but i'm trying to get the program working along the x axis first), basically the first two sweep the x and y coordinates and the other 2 do the checking, so how do I exit the first two loops while leaving the other two running.

    Code:
    
     for ( horizontal_position = 0; horizontal_position <=width;horizontal_position = horizontal_position + step_size)
            {
              counter=0;  //intializing counter value for each postion
              steps=0;
              
              motion(horizontal_position,carrier_position_x);// carrier position in 1 ps steps
              steps++;        
                       
             for(array_position=1;array_position<=11;array_position++)// check for all lattice sites
             {
              
              for(i=1;i<=101;i++)// check all positions the carrier will be in
              {
                               
               vector[1][1]=lattice_points[array_position][1]-carrier_position_x[i];//x position 
               cout<<vector[1][1]<<" "<<lattice_points[array_position][1]<<" "<<carrier_position_x[i]<<" "<<array_position<<" "<<horizontal_position<<endl;
               
               vector[2][1]=lattice_points[array_position][2]-vertical_position;//y position
             
               modulus=sqrt(pow(vector[1][1],2)+pow(vector[2][1],2));
             
             //cout<<vector[1][1]<<" "<<vector[2][1]<<" "<<modulus<<" "<<counter<<" "<<steps<<endl;
               
               if (modulus<radius)
               {
                counter++; 
                 break;   
                    
               }
                            
               
              }//for loop finish checking the trajectory of the carrier           
             }// for loop finish checking all lattice sites 
            
            }
    This code manages to exit the inner most for loop , ie
    Code:
    for(i=1;i<=101;i++)
    but the middle one i.e.
    Code:
    for(array_position=1;array_position<=11;array_position++)
    does not stop.

    Any ideas on how to stop the second loop, while leaving the first one,i.e.
    Code:
    for ( horizontal_position = 0; horizontal_position <=width;horizontal_position = horizontal_position + step_size)
    running.

    TIA
    Last edited by a1pro; 04-29-2005 at 04:10 AM.

  5. #5
    Sweet
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    There is indeed a goto in C++ just like in basic. As 7stud was saying most people tend to look down on goto because it leads to bad style and can make it hard to see what is going on in your code. Others say goto has its advantages to break out of deeply nested loops.

    So my advice for you is to stay away from goto until you are more experienced and than would know when it could be useful for you and use functions instead of goto.
    Woop?

  6. #6
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    never mind
    i got it working now

    inner most loop is a do-while loop now

  7. #7
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    Sorry for hijacking, but is there a replacement for goto loops?

    Code:
          if (opt == "1")
          {
                  long int a = 1;
                  char* newchar;
                  int z;
                  cout<<"Please input integer: ";
                  cin>>newchar;
                  z = atoi(newchar);  
                  cin.ignore();  
                            
                  /*while (!(cin>>z))
                  {
                        cout<<"Please do not input alphabets.\n\n";
                        cin.clear();
                        cin.ignore(std::numeric_limits < int >::max(), '\n');
                        goto end;
                  }*/
    
                  if (z > 1000000)
                  {
                        cout<<"Please do not enter numbers larger than 1,000,000.  \n\n";
                       // cin.get();
                        goto end;    
                  } 
                  cout<<"\nConfirm? (y/n): ";
                  cin>>dozza;
                  cin.get();
                  //getline(cin, dozza, '\n');
                  if ((dozza == "y") || (dozza == "Y"))
                  {
                           b = 1;
                           z = z*80899;
                           _ftime(&sb);
                           start = sb.time*1000 + sb.millitm;
                           while (b <= z)
                           {
                                   bench1(a);
                                   b++;
                           }
                           _ftime(&eb);
                           end = eb.time*1000 + eb.millitm;
                           float x = (end - start);
                           float y = x/1000;
                           cout << "Benchmark took " << y << " seconds\n\n";
                           cout<<"Export results? (y/n): ";
                           cin>>exp;
                           if (exp == "y")
                           {
                                        time(&timz);
                                        ofstream exp("export.txt", ios::app);
                                        std::string thetime = ctime(&timz);
                                        thetime.erase(thetime.find('\n', 0), 1);
                                        exp<<"("<<thetime<<") Integer Benchmark: "<<y<<" seconds.\n";
                                        exp.close();
                                        cout<<"Exported results successfully. Please see export.txt.\n\n";
                           }
                           cin.get();
                  }
    Basically, goto end; goes to the part where it asks to do another calculation. Is there anyway to achieve this without goto loops?

  8. #8
    & the hat of GPL slaying Thantos's Avatar
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    yes but it may well require you rethink the structure

  9. #9
    Registered User Queatrix's Avatar
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    I noticed that everyone says "Don't use Gotos!" but why? Why are they bad?!?!

  10. #10
    & the hat of GPL slaying Thantos's Avatar
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    Read the faq

  11. #11
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    Break deeply nested loops into separate functions.

    Use a flag to break out of necessary nested loops.

    Using goto is acceptable if you are a competent, experienced programmer with specific reasons for it. Unfortunately, beginners like to use it as an "easy" way out and write code that is hard to read, understand and maintain. If you are asking C++ questions on this site, I can almost guarantee that you should not be using goto.

  12. #12
    He's trying.
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    Quote Originally Posted by Cool-August
    I noticed that everyone says "Don't use Gotos!" but why? Why are they bad?!?!
    GOTOs jump around in your code, are confusing to deal with, and when you need to change something it can be very difficult.

    Functions are better because they can use parameters, return specific values (side effects are usu. intentional & obvious), and use local variables.


    Plus they just keep your code all in one spot and better structured.
    Right?

  13. #13
    Registered User Kirdra's Avatar
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    He didn't ask for reasons not to use it, yes, goto is shunned but it has its uses, particularly for optimisations.

  14. #14
    Toaster Zach L.'s Avatar
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    I doubt that you'll optimize much/any using goto. Modern compilers are pretty good at keeping code rather efficient.
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