Thread: simple question for a beginner with arrays

  1. #1
    Registered User
    Join Date
    Apr 2012
    Posts
    3

    simple question for a beginner with arrays

    this is the exercise i am having difficulty with:
    Write a function that prints the values stored in an array of doubles containing n elements. The
    function prototype is:
    void print_array(double x[], int n);
    The required format for the output is [elem0 elem1 elem2 ... elemn-1]; that is, a list
    of values enclosed in square brackets, with one space between each pair of values. There miust
    be no spaces between the '[' and the first value, or between the last value and ']'. Here is an
    example: [1.0 5.2 -3.7 4.9].
    Write a main function that exercises print_array.

    and this is the code i have so far:

    Code:
    void print_array (double x[], int n){
    
        int i=0;
    
            for (x[i];i<n;i++){
                
                if (x[0]){ 
                    printf("[%d ", x[0]);
                }
                else if (x[n-1]) {
                    printf("%d]\n",x[n-1]);
                }
                else {
                    printf("%d ", x[i]);
                }
        
            }
    
    }
    i believe that my code is correct, but an not sure how to test it. i am having problems with the last part of the problem "Write a main function that exercises print_array."
    Anyway, thanks in advanced!!

  2. #2
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    28,413
    Quote Originally Posted by Student12321
    and this is the code i have so far:
    You will find it easier to print the '[' and ']' before and after the loop, respectively. Your checks for x[0] is wrong. Your checks should be concerned with the index or with n, not with the value of the elements.

    Furthermore, you can simplify the logic by just printing the first element, if it exists, then by printing the remaining elements with the " %d" format string.

    Quote Originally Posted by Student12321
    i believe that my code is correct, but an not sure how to test it. i am having problems with the last part of the problem "Write a main function that exercises print_array."
    This is just a matter of creating an array and calling the function.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Registered User
    Join Date
    Apr 2012
    Posts
    3
    thanks, im not quite clear, but ill fiddle around with it.

    what did you mean at the part i bolded?
    Quote Originally Posted by laserlight View Post
    You will find it easier to print the '[' and ']' before and after the loop, respectively. Your checks for x[0] is wrong. Your checks should be concerned with the index or with n, not with the value of the elements.

  4. #4
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    28,413
    Quote Originally Posted by Student12321
    what did you mean at the part i bolded?
    Suppose x[0] is 0. Then your code will not print '[', because 0 evaluates to false.

    EDIT:
    Also, to print a double, you should use %f not %d.
    Last edited by laserlight; 04-08-2012 at 11:31 AM.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
    Registered User
    Join Date
    Apr 2012
    Posts
    3
    hello again, i got it working but i have a question to clear up:
    how come the first case works here, but the second case does not?
    Code:
        int sum
        int i=0;
            printf("[");
            for (x[i];i<n;i++){
                
    
                if (i==n-1) {
                sum=x[n-1];
                    printf("%d]\n",sum);
                }
                else {
                sum=x[i];
                    printf("%d ", sum);
                }
        
            }
    
    }
    Code:
        int sum
        int i=0;
            printf("[");
            for (x[i];i<n;i++){
                
    
                if (i==n-1) {
                                printf("%d]\n",x[n-1]);
                }
                else {
                    printf("%d ", x[i];
                }
        
            }
    
    }

  6. #6
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    28,413
    It looks like it should work in both cases, once you fix the syntax errors. By the way, writing x[i] as the first statement of the for loop is pointless.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Beginner pointers/arrays question
    By whiteandnerdy in forum C Programming
    Replies: 3
    Last Post: 07-14-2010, 02:19 PM
  2. Simple Scanf question for beginner
    By somekid413 in forum C Programming
    Replies: 1
    Last Post: 12-15-2009, 04:56 PM
  3. Beginner's question concerning pointers and arrays
    By rcomj in forum C Programming
    Replies: 5
    Last Post: 08-11-2009, 09:09 AM
  4. Simple stupid question from a beginner
    By oyerth in forum C++ Programming
    Replies: 1
    Last Post: 04-07-2002, 06:32 PM
  5. A simple c++ question..Im a beginner
    By Unregistered in forum C++ Programming
    Replies: 1
    Last Post: 12-04-2001, 04:25 PM