Function problem

[Russco]

I would like some advice. I would like to reduce the use of goto in this function even though it's fairly simple. What if I wanted to reuse bits and pieces of code? Can I do that or once I get into If / else or While loops do I need to move the code pieces inside the loop till it breaks out or what not. It seems kind of pointless to duplicate the code. I guess that is why the goto is so appealing in this type of instance.

int add()
{
        char answer;
        int a,b;
        int total;
 
        start:
 
        std::cout<<"Enter first number: ";
        std::cin>>a;
        std::cout<<"Enter Second number: ";
        std::cin>>b;
 
        total = a+b;
        std::cout<<"\nSum: "<< total <<"\n\n";
 
        question:
        std::cout<<"Do you wish to continue: Y/N ";
        std::cin>>answer;
 
        switch (answer)
        {
                case 'y': goto start;
                case 'Y': goto start;
                case 'n': goto end;
                case 'N': goto end;
                default:
                std::cout<<"Invalid characters.  Use Y/N or y/n.\n\n";
                goto question;
        }
 
        end:
        std::cout<<"Returning to menu";
        sleep(3);
        return 0;
}

would it be bad if I did cases like this?

 case 'y' || 'Y': code sample here

My Goal is to consolidate the code down as small as possible while still being functional.

My god, this is C++ not BASIC. Remove those gotos and replace them with loops and conditionals.
C++ supports 3 types of loop, they are counted (for loop), top tested (while loop ) and bottom tested (do/while loop).

for( int i = 0; i < 10; ++i )
{
   // executed 10 times
}
 
while( variable != value )
{
   // executes while variable is not equal to value
}
 
do
{
 // always executes once, and maybe more
} while ( variable != value );

All better choices than a goto!

[Paul McKenzie]

I would like some advice. I would like to reduce the use of goto in this function even though it's fairly simple.

No, you should eliminate all of the goto's, not just reduce them.

Secondly, a program riddled with goto's are not "simple". It's simple because you put them in, but most programmers who look at your code will not put any effort into understanding it if it has goto's in it.

Look at this example (not compiled):

#include <iostream>

char getResponse()
{
   char answer;
   bool inputOK = false;
   do
   {
        std::cout<<"Do you wish to continue: Y/N ";
        std::cin>>answer;
        switch (answer)
        {
           case 'y': 
           case 'Y':
           case 'n':
           case 'N':
                 inputOK = true;
            break;
            default:
                std::cout<<"Invalid characters.  Use Y/N or y/n.\n\n";
         }
     } while ( !inputOK );
     return answer;
}

int add()
{
        char answer;
        int a,b;
        int total;
        
        do
        {  
            std::cout<<"Enter first number: ";
            std::cin>>a;
            std::cout<<"Enter Second number: ";
            std::cin>>b;

            total = a+b;
            std::cout<<"\nSum: "<< total <<"\n\n";
            answer = getResponse();
        } while (answer == 'Y' || answer == 'y');
        std::cout<<"Returning to menu";
        return 0;
}

Just add a function to get the response. Then the code doesn't turn into spaghetti using goto's.

http://en.wikipedia.org/wiki/Spaghetti_code

Regards,

Paul McKenzie

[fuzzylr]

No, you should eliminate all of the goto's, not just reduce them.

Secondly, a program riddled with goto's are not "simple". It's simple because you put them in, but most programmers who look at your code will not put any effort into understanding it if it has goto's in it.

Look at this example (not compiled):

#include <iostream>

char getResponse()
{
   char answer;
   bool inputOK = false;
   do
   {
        std::cout<<"Do you wish to continue: Y/N ";
        std::cin>>answer;
        switch (answer)
        {
           case 'y': 
           case 'Y':
           case 'n':
           case 'N':
                 inputOK = true;
            break;
            default:
                std::cout<<"Invalid characters.  Use Y/N or y/n.\n\n";
         }
     } while ( !inputOK );
     return answer;
}

int add()
{
        char answer;
        int a,b;
        int total;
        
        do
        {  
            std::cout<<"Enter first number: ";
            std::cin>>a;
            std::cout<<"Enter Second number: ";
            std::cin>>b;

            total = a+b;
            std::cout<<"\nSum: "<< total <<"\n\n";
            answer = getResponse();
        } while (answer == 'Y' || answer == 'y');
        std::cout<<"Returning to menu";
        return 0;
}

Just add a function to get the response. Then the code doesn't turn into spaghetti using goto's.

http://en.wikipedia.org/wiki/Spaghetti_code

Regards,

Paul McKenzie

Thank you. That is definitely some food for thought. Great examples.

[fuzzylr]

I used your code as a base. Pretty much used it entirely. For practice. I have seem to hit a snag. Not sure why. The last part of the code is being skipped.

int add()
{
        char answer;
        int a,b;
        int total;

        do
        {
                std::cout<<"Enter first number: ";
                std::cin>>a;
                std::cout<<"Enter Second number: ";
                std::cin>>b;

                // Add to Int's together.
                total = a+b;
                std::cout<<"\nSum: "<< total <<"\n\n";

                answer = getResponse();
        } while (answer == 'Y' || answer == 'y');
        std::cout<<"Returning to menu";
        sleep(3);
        return 0;
}

This code is only partically being processed...

while (answer == 'Y' || answer == 'y');
        std::cout<<"Returning to menu"; <---- this piece
        sleep(3);
        return 0;
}

What is odd is the sleep is being processed but the cout is not.

[Richard.J]

std::cout<<"Returning to menu" << std::endl;

[fuzzylr]

std::cout<<"Returning to menu" << std::endl;

Is there any difference between

 std::endl

and

\n

When should which be used?

http://www.cplusplus.com/forum/beginner/7350/

I found the link above but I can't seem to find anything saying that they are really all that different.

[Richard.J]

they both add a newline to the buffer, but std::endl flushes the buffer. I.e. when using \n, you'll never know when the buffer is actually sent to the console (assuming std::cout is used) whereas std::endl enforces this.

[fuzzylr]

they both add a newline to the buffer, but std::endl flushes the buffer. I.e. when using \n, you'll never know when the buffer is actually sent to the console (assuming std::cout is used) whereas std::endl enforces this.

Thank you very much.

[Amleto]

This code is only partically being processed...

while (answer == 'Y' || answer == 'y'); <---- semi colon here is bad
        std::cout<<"Returning to menu"; <---- this piece
        sleep(3);
        return 0;
}

What is odd is the sleep is being processed but the cout is not.

.....

[Lindley]

In most cases it doesn't really matter when the output buffer gets flushed, since it will certainly be flushed at the end of the program or upon trying to get any user input. There are a few cases where it does matter (inter-process communication, for instance), so it's good to know what flushing is all about.

[fuzzylr]

.....

Yes it does belong there. It will throw compiler errors or should I say it did toss compiler errors.

also note stated reference below that do-while loops are built that way.

http://www.cplusplus.com/doc/tutorial/control/