Question

Write C functions to do each of the following. Make sure your function has exactly the same name, parameters, and return type as specified here. Please place all of the functions in a single .c file and write a main() to test them.

1. int process(const char *input_filename, const char *output_filename) — reads the file named input_filename and processes it, putting results in output_filename. The input file consists of lines of the form "number operation number," for example:

   15 - 4
   3.38 / 2.288
   2 ^ -5
   35.2 + 38

   The possible operations are +, -, *, /, and ^ (power). Your function should calculate the value of each line's expression and save it (one to a line) to the output file. For example, the input file shown above would result in an output file of

   11.000000
   1.477273
   0.031250
   73.200000

   The return value of the function should be the number of calculations that it did (4 for this example file).

   (Hints: fscanf() returns the constant value EOF when the end of file is reached. The pow(x, y) function defined in <math.h> calculates x^y; you will need to add -lm to the command line when compiling your code to link the math library.)

Answer 1

#include<stdio.h>
#include<math.h>

//function to process input file
int process(const char *input_filename, const char *output_filename) {
  
   //declaring file pointers and opeing file in appropriate modes
   FILE *inp;
   inp = fopen(input_filename, "r");
  
   FILE *outp;
   outp = fopen(output_filename, "w");
   double op1 = 0, op2 = 0;
   char opr
  
   //reading the input file
   while(fscanf(inp, "%lf %c %lf", &op1, &opr, &op2) == 3) {
       double res;
      
       //doing operation as per the operator found
       switch(opr) {
           case '+':
               res = op1 + op2;
               break;
           case '-':
               res = op1 - op2;
               break;
           case '*':
               res = op1 * op2;
               break;
           case '/':
               res = op1 / op2;
               break;
           case '^':
               res = pow(op1, op2);
               break;
       }
       //writing the result onto the output file.
       fprintf(outp, "%lf\n", res);
   }
  
   fclose(inp);
   fclose(outp);
     
}

main() {
   process("input.txt", "output.txt");
}

Input.txt

15 - 4
3.38 / 2.288
2 ^ -5
35.2 + 38

output.txt

11.000000
1.477273
0.031250
73.200000