how to exit nested loops

Question

i have something like

   while(playAgain==true)
   {
      cout<<"new game"<<endl; //i know 'using namespace std;' is looked down upon
      while(playerCard!=21)
      {
          *statements*
          if(decision=='n')
          {
              break
          }
       ...
      }
   }

but that break only breaks out of the first while loop when I want to break out of both of the loops

You could use a goto statement which jumps to a label outside the loop.... Of course im joking :). The best solution is to avoid the nested if (The if with the break) and put the condition (decission == 'n') in the two loops. — Manu343726
– Manu343726, Commented Sep 7, 2013 at 6:35

LihO · Accepted Answer · 2013-09-07 05:29:51Z

7

Don't cook spaghetti and extract your loops into the function:

void foo(...) {
    while (...) {
        /* some code... */
        while (...) {
            if ( /* this loop should stop */ )
                break;
            if ( /* both loops should stop */ )
                return;
        }
        /* more code... */
    }
}

this decomposition will also yield cleaner code since instead of hundreds of lines of ugly procedural code, you will have neat functions at different levels of abstraction.

edited Sep 7, 2013 at 5:29

answered Sep 7, 2013 at 5:24

LihO

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1 Comment

Robin Hsu Over a year ago

It has a shortfall when too many variables are used but defined outside of the loop (in the original function), which means you have to pass those many variables via foo()'s arguments

Eric Z · Accepted Answer · 2013-09-07 05:32:08Z

4

There are basically two options to go.

Add the condition check in outer loop.

while ((playAgain==true) && (decision != '\n'))
Simply use goto. People are often told never to use goto as if it's monster. But I'm not opposed to use it to exit multiple loops. It's clean and clear in this situation.

edited Sep 7, 2013 at 5:32

answered Sep 7, 2013 at 5:26

Eric Z

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1 Comment

Silidrone Over a year ago

+1 for the goto comment, people are often mindlessly rejecting the idea of some concepts, like goto. There are cases in which it is completely fine to use it.

cpp · Accepted Answer · 2013-09-07 05:27:22Z

1

Use goto:

   while(playAgain==true)
   {
      cout<<"new game"<<endl; //i know 'using namespace std;' is looked down upon
      while(playerCard!=21)
      {
          *statements*
          if(decision=='n')
          {
              goto label;
          }
       ...
      }
   }
   label: 
   ...

answered Sep 7, 2013 at 5:27

cpp

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Comments

P0W · Accepted Answer · 2013-09-07 05:39:41Z

1

 while(playAgain==true && decision !='n' ){
                           ^^ add a condition
      cout<<"new game"<<endl; 
      while(playerCard!=21){
      *statements*
      if(decision=='n'){
          break
         }
     ...
      }
 }

edited Sep 7, 2013 at 5:39

answered Sep 7, 2013 at 5:26

P0W

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Comments

thefourtheye · Accepted Answer · 2013-09-07 05:26:50Z

0

This solution is specific to your case. When the user's decision is 'n', he doesn't want to play again. So just set playAgain to false and then break. Outer loop will be broken automatically.

while(playAgain==true){
   cout<<"new game"<<endl; //i know 'using namespace std;' is looked down upon
   while(playerCard!=21){
      *statements*
      if(decision=='n'){
         playAgain = false; // Set this to false, your outer loop will break automatically
         break;
      }
   }
}

answered Sep 7, 2013 at 5:26

thefourtheye

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Comments

qsona · Accepted Answer · 2013-09-07 05:30:57Z

0

If you don't have to avoid goto statement, you can write

while (a) {
    while (b) {
        if (c) {
            goto LABEL;
        }
    }
}
LABEL:

answered Sep 7, 2013 at 5:30

qsona

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