While Loop

This is a discussion on While Loop within the C++ Programming forums, part of the General Programming Boards category; I am trying to iterate through two list objects representing polynomials to perform a multiplication operation. But I have been ...

  1. #1
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    While Loop

    I am trying to iterate through two list objects representing polynomials to perform a multiplication operation. But I have been unable to fix the problem with the while loop because it never enters the nested for loops and size never gets decremented and I get an infinite loop. Can someone point me in the right direction? Thanks.

    Code:
     int size = b.PolyTerms.size();
     while(!size < 0)
     {
      for(It = tmpPoly.PolyTerms.begin(); It != tmpPoly.PolyTerms.end(); ++It)
      {       
       for(It2 = tmpPoly2.PolyTerms.begin(); It2 != tmpPoly2.PolyTerms.end(); ++It2)       
       {
        exp = (*It) + (*It2);
        size--;
        
        ++It;
        ++It2; 
       
        coeff = (*It) * (*It2);
         
        tPoly.PolyTerms.push_back(exp);
        tPoly.PolyTerms.push_back(coeff);
        
        size--;  
        
        //reset It iterator to first term since there are still more terms to multiply
        //in the second polynomial
        It = tmpPoly.PolyTerms.begin();    
       }
      }
      
     }//end while
      //Post-Condition: size < 0 so all of the terms in the second polynomial have  
      //been multiplied by the first term of the first polynomial. Repeat the 
      //process for the next term.             
     
    ...

  2. #2
    Just Lurking Dave_Sinkula's Avatar
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    By this
    Code:
    while(!size < 0)
    I'm guessing you mean 'while size is not less than zero'. This is normally written as
    Code:
    while(size >= 0)
    That is, "while size is greater than or equal to zero".

    !size will either evaluate to 1 or 0, neither of which will ever be less than zero.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  3. #3
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    Oh yes. But I did that to test to see If I could determine what was being executed and what was not. I even tried while (size >0) and for some reason, the for loops are not being executed.

  4. #4
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    Output b.PolyTerms.size(), tmpPoly.PolyTerms.size(), and tmpPoly2.PolyTerms.size() before the while loop. One of them will probably be zero. If all are greater than zero (and you use while (size > 0)) then you should be at least entering the nested for loops.

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