CS10 SI Classroom Session 3 - Calculator

main.cpp

#include <iostream>
// Remember to include cmath for math functions
#include <cmath>

using namespace std;

int main() {
  // Most math functions deal with doubles so we might as well make it easy.
  double leftOperand = 0.0, rightOperand = 0.0;
  double result = 0.0;
  const double PI = 3.14159265, TO_RAD = PI / 180;
  string operation = "";

  cout << "Welcome to easy_calc, a simple calculator!" << endl;
  cout << "You can perform any math operation possible by the functions "
          "in the cmath library." << endl << endl;

  cout << "To use this, simply enter in two floating point numbers and an "
       << "operator. For example, to compute 3^4, enter \"3 4 pow\""
       << endl << endl;

  cout << "If the math calculation you want to compute only takes one operand, "
       << "enter two numbers and an operator and only the first number will be "
       << "used." << endl;

  cout << "Enter two floating points numbers and an operator: ";
  cin >> leftOperand >> rightOperand >> operation;

  if (operation == "+") {
    result = leftOperand + rightOperand;
  } else if (operation == "-") {
    result = leftOperand - rightOperand;
  } else if (operation == "*") {
    result = leftOperand * rightOperand;
  } else if (operation == "/") {
    // Sometimes if might be useful to have if statements inside of if 
    // statements. This is called nesting if statements.
    if (rightOperand != 0.0) {
      // Now we can avoid those pesky logical errors.
      result = leftOperand / rightOperand;
    } else {
      cout << "I can't divide by 0!" << endl;
    }
  } else if (operation == "%") {
    if (rightOperand != 0.0) {
      // Remember, remainders only exist in integer division.
      result = static_cast<int>(leftOperand) % static_cast<int>(rightOperand);
    } else {
      cout << "I can't divide by 0!" << endl;
    }
  } else if (operation == "abs") {
    result = abs(leftOperand);
  } else if (operation == "sin") {
    // Operations like sin, cos, and tan take in radians instead of degrees.
    result = sin(leftOperand * TO_RAD);
  } else if (operation == "cos") {
    result = cos(leftOperand * TO_RAD);
  } else if (operation == "tan") {
    result = tan(leftOperand * TO_RAD);
  } else if (operation == "pow") {
    result = pow(leftOperand, rightOperand);
  } else if (operation == "sqrt") {
    if (leftOperand >= 0.0) {
      result = sqrt(leftOperand);
    } else {
      cout << "Woah, is the square root of " << leftOperand << " even real?\n";
    }
  } else if(operation == "log") {
    if (leftOperand > 0.0) {
      result = log(leftOperand);
    } else {
      cout << "You can only take the log of positive numbers. "
	   << "And 0 isn't positive." << endl;
    }
  } else if (operation == "exp") {
    result = exp(leftOperand);
  } else {
    // The default in case we don't know about the operation.
    cout << "I'm not familiar with how to perform a " << operation
	 << ". Make sure you spelled it correctly and try again." << endl;
  }

  cout << endl << "If everything went fine, your result is " << result << endl;

  return 0;
}