Loop skip problem

This is a discussion on Loop skip problem within the C++ Programming forums, part of the General Programming Boards category; Hi guys I am having a problem with a peice of code. The program compiles ok ( I do get ...

  1. #1
    Its hard... But im here swgh's Avatar
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    Loop skip problem

    Hi guys

    I am having a problem with a peice of code. The program compiles ok ( I do get a warning about a mis-match '<' type in the for loop ).

    Basically, I am trying to read in 10 scores per student, calculate the average and pass it to a vector. Now, this all seems to be working fine, but when I have read in the final grade for the first student, it terminates with no reason ( I get no seg-fault error so it isnt that ) and doesnt go to the next student.

    Here is my code

    Code:
    // function to input 10 test scores and calculate
    // the average of the scores per student
    void GradeBook::inputGrades( const std::vector<std::string> &rStuNm )
    {
    	int counter = 1;
    	int totalScore = 0;
    	int result = 0;
    	double average = 0;
    
    	// read in 10 scores per student
    	for ( int i = 0; i < rStuNm.size(); )
    	{
    		while ( counter <= 10 )
    		{
    			std::cout << "Enter grade[ " << counter << " ] for student "
    					  << rStuNm[ i ] << " : ";
    			std::cin >> result;
    
    			totalScore += result;
    			counter++;
    		}
    		
    		// calculate the average for this student
    		average = totalScore / counter;
    		
    		// place claculated average in vector
    		m_AverageOfResults.push_back ( average );
    
    		// goto the next student
    		i++; // THIS IS NOT BEING READ?
    	}
    }
    Oh, and the constructor is:

    Code:
    GradeBook::GradeBook ( std::string name ) :
    	m_Students ( m_MAX_VECTOR, "" ),
    	m_AverageOfResults ( m_MAX_VECTOR, 0 ),
    	m_LetterGrade ( m_MAX_VECTOR, '\0' ),
    	m_CourseTaken ( m_MAX_VECTOR, "" ) ...
    In case the helps. MAX_VECTOR has a value of 10 btw

    Any help appreiciatred. It looks like somthing very simple I am doing wrong.
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  2. #2
    Kernel hacker
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    You are going over the limit of your vector:
    Code:
    while ( counter <= 10 )
    will allow the loop to continue until counter == 11, which causes the vector to overrun.

    I would also like to change your multiple vectors: Why not have a single vector of
    Code:
    struct GradeRecord
    {
        std::string name;
        double AverageOfResults;
        char LetterGrade;
        std::string CourseTaken;
    }
    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Registered User
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    Why are you incrementing the loop counter in the body of the loop?

  4. #4
    Kernel hacker
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    And medievalelks comments made me look again on the code - you won't ever read the second students grades. You may want to use a traditional for-loop for that too.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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