C PROGRAMMING  HELP I'm trying to get a portion of my script to work as a udf inside of a header file that already contains two other udfs that are working properly.  Here is the script with // lines saying the start and end of the portion i want to be a udf in the header file that I will also paste below the script. Script: #include #include #include "PROJECT HEADER2.h"     int main() {     // Open the input file     FILE *input_file = fopen("Data.txt", "r");     if (input_file == NULL) {         printf("Error: could not open input file\n");         return 1;     }     // Open the output file     FILE *output_file = fopen("Result.txt", "w");     if (output_file == NULL) {         printf("Error: could not open output file\n");         fclose(input_file);         return 1;     } //EVERYTHING STARTING HERE     // Read the input file and compute coefficients for each line     int line_count = 0;     double a1, a2, y0, y_prime0, lambda1, lambda2, C1, C2, C_alpha, theta;     while (fscanf(input_file, "%lf %lf %lf %lf", &a1, &a2, &y0, &y_prime0) == 4) {         // Compute the roots of the equation         double discriminant = a2 * a2 - 4 * a1;         // Complex roots         if (discriminant < 0) {                  lambda1 = -a2 / (2 * a1);             lambda2 = sqrt(-discriminant) / (2 * a1);         // Repeated real roots         } else if (discriminant == 0) {                  lambda1 = lambda2 = -a2 / (2 * a1);         // Distinct real roots         } else {              lambda1 = (-a2 + sqrt(discriminant)) / (2 * a1);             lambda2 = (-a2 - sqrt(discriminant)) / (2 * a1);         } //AND ENDING HERE I WANT IN HEADER FILE         // Compute coefficients and write output to file based on type of roots         compute_coefficients(lambda1, lambda2, &C1, &C2, &C_alpha, &theta);         fprintf(output_file, "%d %lf %lf\n",              (lambda1 == lambda2) ? 2 : ((fabs(lambda1 - lambda2) < 1e-10) ? 1 : 3),             (lambda1 == lambda2) ? C1 : ((fabs(lambda1 - lambda2) < 1e-10) ? C1 : C_alpha),             (lambda1 == lambda2) ? C2 : ((fabs(lambda1 - lambda2) < 1e-10) ? C2 : theta)         );         display_output(lambda1, lambda2, C1, C2, C_alpha, theta);         line_count++;     }     // Close the input and output files     fclose(input_file);     fclose(output_file);     return 0; } Header File: #ifndef PROJECT_HEADER2_H #define PROJECT_HEADER2_H //Calculation function void compute_coefficients(double lambda1, double lambda2, double *C1, double *C2, double *C_alpha, double *theta) {     if (lambda1 == lambda2) {      // Repeated real roots         *C1 = 1;         *C2 = 0;         *C_alpha = lambda1;         *theta = 0;     } else if (fabs(lambda1 - lambda2) < 1e-10) {      // Distinct real roots (with rounding tolerance)         *C1 = 1;         *C2 = lambda1;         *C_alpha = 0;         *theta = 0;     } else {      // Distinct real roots         *C1 = (lambda2 - 1) / (lambda2 - lambda1);         *C2 = (1 - lambda1) / (lambda2 - lambda1);         *C_alpha = (lambda1 - lambda2) / (lambda2 - 1);         *theta = atan2(1 - lambda1, lambda2 - 1);     } } //Print function void display_output(double lambda1, double lambda2, double C1, double C2, double C_alpha, double theta) {     printf("lambda1 = %lf\n", lambda1);     printf("lambda2 = %lf\n", lambda2);     printf("C1 = %lf\n", C1);     printf("C2 = %lf\n", C2);     printf("C_alpha = %lf\n", C_alpha);     printf("theta = %lf\n", theta); } #endif

C PROGRAMMING  HELP

I'm trying to get a portion of my script to work as a udf inside of a header file that already contains two other udfs that are working properly. 

Here is the script with // lines saying the start and end of the portion i want to be a udf in the header file that I will also paste below the script.

Script:

#include <stdio.h>
#include <math.h>
#include "PROJECT HEADER2.h"    

int main()
{
    // Open the input file
    FILE *input_file = fopen("Data.txt", "r");
    if (input_file == NULL) {
        printf("Error: could not open input file\n");
        return 1;
    }

    // Open the output file
    FILE *output_file = fopen("Result.txt", "w");
    if (output_file == NULL) {
        printf("Error: could not open output file\n");
        fclose(input_file);
        return 1;
    }
//EVERYTHING STARTING HERE
    // Read the input file and compute coefficients for each line
    int line_count = 0;
    double a1, a2, y0, y_prime0, lambda1, lambda2, C1, C2, C_alpha, theta;
    while (fscanf(input_file, "%lf %lf %lf %lf", &a1, &a2, &y0, &y_prime0) == 4) {
        // Compute the roots of the equation
        double discriminant = a2 * a2 - 4 * a1;
        // Complex roots
        if (discriminant < 0) {     
            lambda1 = -a2 / (2 * a1);
            lambda2 = sqrt(-discriminant) / (2 * a1);
        // Repeated real roots
        } else if (discriminant == 0) {     
            lambda1 = lambda2 = -a2 / (2 * a1);
        // Distinct real roots
        } else { 
            lambda1 = (-a2 + sqrt(discriminant)) / (2 * a1);
            lambda2 = (-a2 - sqrt(discriminant)) / (2 * a1);
        }
//AND ENDING HERE I WANT IN HEADER FILE
        // Compute coefficients and write output to file based on type of roots
        compute_coefficients(lambda1, lambda2, &C1, &C2, &C_alpha, &theta);
        fprintf(output_file, "%d %lf %lf\n", 
            (lambda1 == lambda2) ? 2 : ((fabs(lambda1 - lambda2) < 1e-10) ? 1 : 3),
            (lambda1 == lambda2) ? C1 : ((fabs(lambda1 - lambda2) < 1e-10) ? C1 : C_alpha),
            (lambda1 == lambda2) ? C2 : ((fabs(lambda1 - lambda2) < 1e-10) ? C2 : theta)
        );
        display_output(lambda1, lambda2, C1, C2, C_alpha, theta);
        line_count++;
    }

    // Close the input and output files
    fclose(input_file);
    fclose(output_file);

    return 0;
}

Header File:

#ifndef PROJECT_HEADER2_H

#define PROJECT_HEADER2_H

//Calculation function
void compute_coefficients(double lambda1, double lambda2, double *C1, double *C2, double *C_alpha, double *theta)
{
    if (lambda1 == lambda2) { 
    // Repeated real roots
        *C1 = 1;
        *C2 = 0;
        *C_alpha = lambda1;
        *theta = 0;
    } else if (fabs(lambda1 - lambda2) < 1e-10) { 
    // Distinct real roots (with rounding tolerance)
        *C1 = 1;
        *C2 = lambda1;
        *C_alpha = 0;
        *theta = 0;
    } else { 
    // Distinct real roots
        *C1 = (lambda2 - 1) / (lambda2 - lambda1);
        *C2 = (1 - lambda1) / (lambda2 - lambda1);
        *C_alpha = (lambda1 - lambda2) / (lambda2 - 1);
        *theta = atan2(1 - lambda1, lambda2 - 1);
    }
}
//Print function
void display_output(double lambda1, double lambda2, double C1, double C2, double C_alpha, double theta)
{
    printf("lambda1 = %lf\n", lambda1);
    printf("lambda2 = %lf\n", lambda2);
    printf("C1 = %lf\n", C1);
    printf("C2 = %lf\n", C2);
    printf("C_alpha = %lf\n", C_alpha);
    printf("theta = %lf\n", theta);
}
#endif

Thank you for your help!