Question

Task C. Calc2: Reading multiple formulas.

Write a better version of the calculator, calc2.cpp, that can evaluate multiple arithmetic expressions. Let’s use the semicolon symbol that must be used at the end of each expression in the input.

Assuming that the input file formulas.txt looks as follows:

15 ;
10 + 3 + 0 + 25 ;
5 + 6 - 7 - 8 + 9 + 10 - 11 ;

When we run the program with that input, the output should evaluate all of the expressions and print them each on its own line:

$ ./calc2 < formulas.txt
15 
38
4

Answer 1

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Program

#include <iostream>
#include<fstream>
using namespace std;

int main() {
   int num;
   char op;
   bool solved = false;
   ifstream infile;
   infile.open("formulas.txt");
   infile>> num;
   int result = num;
   while (infile>> op >> num) { //Inputs operators and the numbers
      
       solved = false;
       if (op == ';') {
           cout << result << endl;
           solved = true;
           result = num;
       }
       if (!solved) {           // Keep calculating until operator is ;
           if (op == '+'){
               result += num;
               solved = true;
           } else if (op == '-'){
               result -= num;
               solved = true;
           }
       }
   }

   if (solved) {
       cout << result << endl;
   }
return 0;
}

Output

15
38
4

formulas.txt

15 ;
10 + 3 + 0 + 25 ;
5 + 6 - 7 - 8 + 9 + 10 - 11 ;