Quick array fix

This is a discussion on Quick array fix within the C Programming forums, part of the General Programming Boards category; This code doesn't seem to be looping properly because it doesn't store the correct array values (in fact, the values ...

  1. #1
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    Quick array fix

    This code doesn't seem to be looping properly because it doesn't store the correct array values (in fact, the values are all set to 0 in the end). And I can't figure out why for the life of me..

    Code:
    for(i=0; i<min_in_trip/5; i++) {
        for(j=0; j<300; j++)
          fscanf(ifp, "%f%f", &temp, &temp2);
          numrevs += temp;
          gas += temp2;
        if(j == 300)
          array[i] = findfueleff(radius, numrevs, gas);
      }
    I really need this to work so that I can finish working on another program for homework that requires that the program that this code was derived from to work.

    Thanks!

    P.S. I have attached the .txt file that this program uses.
    Attached Files Attached Files

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    We like indentation here, but this is not Python, and indentation is no substitute for getting the braces right:
    Code:
    for(i=0; i<min_in_trip/5; i++) {
        for(j=0; j<300; j++) {
          fscanf(ifp, "%f%f", &temp, &temp2);
          numrevs += temp;
          gas += temp2;
        }
        if(j == 300)
          array[i] = findfueleff(radius, numrevs, gas);
      }

  3. #3
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    (1)
    Code:
    >    for(j=0; j<300; j++)
    >      fscanf(ifp, "&#37;f%f", &temp, &temp2);
    >      numrevs += temp;
    >      gas += temp2;
    Assuming you want to sum all 300 items, you're missing some braces:
    Code:
        for(j=0; j<300; j++)
        {
          fscanf(ifp, "%f%f", &temp, &temp2);
          numrevs += temp;
          gas += temp2;
        }
    (2) Make sure temp and temp2 are declared as floats versus doubles, as %f is for reading floats. Use %lf to read doubles instead.

    (3) You should probably check the return of fscanf() to be sure it actually read two floats:
    Code:
          if (fscanf(ifp, "%f%f", &temp, &temp2) == 2)
          {
            /* Sum data */
          }
          else
          {
            /* Data not read */
          }

  4. #4
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    Code:
    /* Definition libraries. */
    #include <stdio.h>
    #include <stdlib.h>
    
    /* Defines constants. */
    #define PI 3.14159
    #define INCHES_IN_FEET 12
    #define FEET_IN_MILE 5280
    
    /* Initializes functions. */
    double findfueleff(double radius, double numrevs, double gas);
    void printGraph(double array[], int length);
    
    int main() {
      
      /* Defines variables. */
      FILE *ifp;
      int i, j;
      int min_in_trip, radius;
      double array[6], temp, temp2, numrevs, gas;
      char filename[20];
      
      /* Checks and opens input file. */
      do {
        printf("Enter the name of the file storing tire gas and tire rotation data.\n");
        scanf("%s", &filename);
        ifp = fopen(filename, "r");
      
        if(ifp == NULL)
          printf("File not found.\n");
      }
      while(ifp == NULL);
      printf("\n");
      
      /* Scans in length of trip and tire radius and determines array length. */
      fscanf(ifp, "%d%d", &min_in_trip, &radius);
      
      /* Scans in values from file. */
      for(i=0; i<min_in_trip/5; i++) {
        for(j=0; j<300; j++) {
          fscanf(ifp, "%lf%lf", &temp, &temp2);
          numrevs += temp;
          gas += temp2;
        }
        if(j == 300)
          array[i] = findfueleff(radius, numrevs, gas);
      }
        
      /* Prints out bar graph to display data. */
      printGraph(array, min_in_trip/5);
      
      /* Closes input file. */
      close(ifp);
      
      system("PAUSE");
      return (0);
    
    }
    
    /* Checks values that calculate fuel efficiency and returns the respective value. */
    double findfueleff(double radius, double numrevs, double gas) {
      if(numrevs == 0 && gas > 0)
        return 100;
      else if(numrevs == 0 && gas == 0) {
        return 0;
      }
      else
        return ((2*PI*radius/INCHES_IN_FEET/FEET_IN_MILE)*numrevs)/gas;
    }
    
    /* Creates bar graph. */
    void printGraph(double array[], int length) {
    
      int i, j;
      
      for(i=95; i>=0; i=i-5) {
        printf("%-4d", i);
        for(j=0; j<length; j++) {
          if(array[j]>=i)
            printf("***** ");
          else
            printf("      ");
        }
        printf("\n");
      }
    
      printf("    ");
      for(i=0; i<=34; i++) {
        printf("-");
      }
      printf("\n");
      printf("    ");
      printf("00-05 05-10 10-15 15-20 20-25 25-30\n");
      printf("\n");
    }
    Still not working with the above attached text file, so I decide to post the entire program instead.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    It would probably be a good idea to initialize numrevs and gas.

  6. #6
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    double array[6], temp, temp2, numrevs, gas; ..?

    ..unless there is something else I need to do.

  7. #7
    and the Hat of Guessing tabstop's Avatar
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    I never said you hadn't declared them, I said you hadn't initialized them. Print the value of numrevs before the for-loop and see what you see.

  8. #8
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    I just understood what you meant, and I set both variables equal to 0.

    But I'm not sure if it is printing the correct information still..

  9. #9
    Algorithm Dissector iMalc's Avatar
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    In your code, when would this ever not be true:
    Code:
        if(j == 300)
    So what is the point in it?
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

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