basic printf and fprintf

Instead of the final print out being: The sum of the dollar amounts is

I would like for it to display: The sum of the (%d how ever many amounts they put in) is

How do you set (the value of how many times the user input a dollar amount to be calculated) to a variable so that it can be referenced in the final printf?

Code:

---

void sumDoubles ()
{
        double num = 0;
        double total = 0;
        int doublesEntered = 0;
        int index;
        double amounts[100];
       
        FILE *myFile;
        myFile = fopen("assignment3.txt", "w");

                printf("\nI want to sum up dollar amounts.\n\n");
                fprintf(myFile, "You chose to sum a list of dollar amounts.\n\nThese are the dollar amounts:\n\n");
       
               
                do
        {       
                printf("\nEnter an dollar amount (enter -1 to quit): \n\n\t\t\t");
                scanf("%lf", &num);
                                       

                        if (num != -1 )
                                {   
                                amounts[doublesEntered] = num;  // store each num in the array
                                doublesEntered++;  // advance the index by 1 for the next num
                       
                                fprintf(myFile, "$%.2f\n", num);
                       
                                total += num;
                                printf("\n\tThe total so far is: $%.2f\n", total);
                                }
               
                        else
               
                                break;
                               
        }        while(num != -1);

       

                                                                for (index = 0; index < num; index++)
                                                                {
                                                                total += amounts[index];
                                                                }



                fprintf(myFile, "\nThe sum of the dollar amounts is $%.2f", total);
                printf("\nThe sum of the dollar amount is $%.2f\n\n\n", total);
                printf("\tThank you for playing!\n\n\n\n");

                fclose(myFile);

        return;
}

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In another words, how can I print the number of elements in the array?

The variable doublesEntered keeps track of the number of values entered. Print its value using the %d format.

Instead of

Code:

---

if (num != -1)

---

try

Code:

---

for(i = 0; i != -1; i++)

---

this will help you keep track of the total number of inputs

hopefully that helps. Im still a rookie so if not my bad.

Quote:

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Originally Posted by grumpy

The variable doublesEntered keeps track of the number of values entered. Print its value using the %d format.

---

Grumpy is right though, doublesEntered keeps track of the number of values entered just as i in my previous post would.

Thanks.

I tried implementing the same fix for my other function and got a negative result. Can anyone help explain why I'm getting the wrong value for the number of elements in the array? And also what I should work on to fix it?

Code:

---

void sumIntegers ()
{
int arr[100];
int i;
int num = 0;
int sum = 0;

FILE *myFile;
myFile = fopen("assignment3.txt", "w");
       

                printf("\nI want to sum up even integers <= 50.\n\n");


                do
        {
                printf("\n\nPlease enter a positive integer:\n\n\t\t\t");
                scanf("%d", &num);
               
                fprintf(myFile, "You chose to sum the even integers from 0 to %d.\n\n", num);
               
               
                        if(num < 0)
                                {
                                printf("\n*** Negative numbers are invalid! ***\n\n\n");
                                break;
                                }
       
                       
                                       
                                                        for (i = num - 4; i >= 0; i--)
                                                        {
                                                        arr[i] = (i + 1) * 2;        // add 1 to the index, then double it, and store that # in arr
                                                        printf ("\nIn index #%d of arr, we stored the value %d.\n", i, arr[i]);    //prints arr[i] with index reference
                                       
                                                        fprintf(myFile, "%d\n\n", arr[i]);    //prints to txt file
                                                        }



                printf("\n");
                                       


                                                        for (i = num - 4; i >= 0; i--)
                                                        {
                                                        sum += arr[i]; // add each element to "sum"
                                                        }


                printf("\n\nThe total of the %d even element in arr[i] = %d.\n\n\n\n", i, sum);
                fprintf(myFile, "The sum of the %d even integers is: %d", i, sum);        //prints to txt file
       
        }        while(num <= 0);


        fclose(myFile);
       
        return;
}

---

Code:

---

    for (i = num - 4; i >= 0; i--)
    {
        sum += arr[i]; // add each element to "sum"
    }
    printf("\n\nThe total of the %d even element in arr[i] = %d.\n\n\n\n", i, sum);

---

Are you aware that this will alwais print

Code:

---

The total of the -1 even element ...

---

because i will always be -1 after the loop.

I do not understand why your loops need to count backwards

Kurt

Quote:

---

Originally Posted by ZuK

Code:

---

    for (i = num - 4; i >= 0; i--)
    {
        sum += arr[i]; // add each element to "sum"
    }
    printf("\n\nThe total of the %d even element in arr[i] = %d.\n\n\n\n", i, sum);

---

Are you aware that this will alwais print

Code:

---

The total of the -1 even element ...

---

because i will always be -1 after the loop.

I do not understand why your loops need to count backwards

Kurt

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Yes I'm aware. I seem to like making things harder than they are and need to be. Why do I tend to figure things out right after I post a thread asking for help?