Chapter 3. Exercise 10. Primitive calculator.

chapter 3/exercise_10.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <cmath>
+
+int main()
+{
+    std::string operation;
+    double operand1, operand2;
+    double result = std::nan("1");
+    bool exit = false;
+
+    std::cout << "Enter the operation and it's two operands please: ";
+    while ( std::cin >> operation >> operand1 >> operand2 )
+    {
+        if ( operation == "+" || operation == "plus" )
+        {
+            result = operand1 + operand2;
+        }
+        else if ( operation == "-" || operation == "minus" )
+        {
+            result = operand1 - operand2;
+        }
+        else if ( operation == "*" || operation == "mul" )
+        {
+            result = operand1 * operand2;
+        }
+        else if ( operation == "/" || operation == "div" )
+        {
+            result = operand1 / operand2;
+        }
+        else
+        {
+            result = std::nan("1");
+        }
+
+        if ( std::isnan(result) )
+        {
+            std::cout << "Error has occured. Try again.\n";
+        }
+        else
+        {
+            std::cout << operand1 << " " << operation << " " << operand2 << " = " << result << ";\n";
+        }
+        std::cout << "Enter the operation and it's two operands please: ";
+    }
+    std::cout << std::endl;
+}

chapter 3/exercise_9.cpp

@@ -3,10 +3,10 @@
 int main()
 {
     std::string number = " ";
-    std::cout << "\nEnter the numerals please: ";
+    std::cout << "Enter the numerals please: ";
     while( std::cin >> number )
     {
-        if ( number == "zero\n" )
+        if ( number == "zero" )
         {
             std::cout << "0\n";
         }