Description: Calculates the integral between 0 and a user defined limit.

Problem: I can't seem to get the validation of temp to work.

cos2.dat:

Program:Code:0.000000 1.000000 0.000157 1.000000 0.000314 1.000000 0.000471 1.000000 0.000628 1.000000 0.000785 0.999999 0.000942 0.999999 0.001100 0.999999 a 0.999998 // test fail point. 0.001414 0.999998 0.001571 0.999998 0.001728 0.999997 0.001885 0.999996 0.002042 0.999996 ....

Code:#include <stdio.h> #include <stdlib.h> #include <math.h> #include <ctype.h> #define max_limit 1.570639 #define limitcheck(x) ((x < 0)||(x > max_limit) ? -1 : x) /* Function prototype */ double integral(double x[], double f[], int N, double *a, double *b); int main(int argc, char* argv[]) { FILE *input; int i=0, N=0, v1=0, v2=0; double a=0, b=0, valid[1], temp, dump, *x, *f, m; const char inp_fn[]="cos2.dat"; char test; if(argc != 2) // Check input. { printf("You have failed to provide the integration limit\n"); exit(EXIT_FAILURE); } else // Read input. { valid[0]=sscanf(argv[1], "%lf", &b); b = limitcheck(b); // Check the limit is within range. /* Open input file */ input = fopen(inp_fn, "r"); if(!valid[0]) // Invalid input. { printf("You have failed to provide a valid integration limit.\n"); exit(EXIT_FAILURE); } else if(b < 0) // Invalid range. { m = max_limit; printf("Please enter integration limit between 0 and %lg.\n", m); exit(EXIT_FAILURE); } else if(input == (FILE*) NULL) // No file. { printf("Input file could not be opened (cos2.dat).\n"); exit(EXIT_FAILURE); } else // Valid. { for(N=0; (b>temp); N++) { fscanf(input, "%lf", &temp); fscanf(input, "%lf", &dump); if( isalpha(temp) ) { printf("Input file was corrupted (cos2.dat).\n"); exit(EXIT_FAILURE); } } rewind(input); // Reset to begining of file. x = malloc((N)*sizeof(double)); // Allocated memory for x. f = malloc((N)*sizeof(double)); // Allocated memory for f. for(i=0; i<(N-1); i++) // Inputing array values. { fscanf(input, "%lf", &x[i]); fscanf(input, "%lf", &f[i]); } /* Close input file */ fclose(input); integral(x,f,N,&a,&b); free(x); // Clearing memory free(f); // Clearing memory exit(EXIT_SUCCESS); } } return(0); } double integral(double x[], double f[], int N, double *a, double *b) { int j=1; double sum=0, h=0; /* Calculating integral */ for (j=1; j <= (N-2); j= j+1) { sum += f[j-1]*(x[j]-x[j-1]); h = (x[j]-x[j-1]); } sum += f[j-1]*(*b-x[j-1]); // Adding final term. printf("Integral of cos^2 between %lf and %lf = %lf\n", *a, *b, sum); // Output }