Make a function to check the validation of input.

CPP019_CalculateArea_Exercise.cpp

@@ -1,96 +1,199 @@
-/**
- * Author:    Tridib Samanta
- * Created:   15.01.2020
- **/
-
 #include<iostream>
+
 #define PI 3.14
+
 using namespace std;
 
-void initMenu();
+
+
+void menu();
+
 void menuDecision(int);
+
 double areaCircle(double);
+
 double areaSquare(double);
+
 double areaRectangle(double,double);
+
 double areaTriangle(double,double);
 
+bool check_for_positive(double);
+
+
 
 int main() {
 
+
+
     int choice;
+
     char cont;
 
+
+
     do {
-        //system("cls");
-        initMenu();
+
+        menu();
+
         cin>>choice;
 
+
+
         menuDecision(choice);
 
+
+
         cout<<"Do you want to continue ? (Y/N)"<<endl;
+
         cin>>cont;
+
     } while(cont=='Y'||cont=='y');
 
+
+
     return 0;
+
 }
 
-void initMenu() {
-    cout<<"Select from the options :"<<endl;
-    cout<<"1.Circle"<<endl;
-    cout<<"2.Square"<<endl;
-    cout<<"3.Rectangle"<<endl;
-    cout<<"4.Triangle"<<endl;
+
+
+void menu() {
+    cout << "____MENU____" << endl;
+
+    cout<<"1. Circle\n2. Square\n3. Rectangle\n4. Triangle"<<endl;
+    cout<<"Enter your choice: ";
+
 }
 
+
+
 void menuDecision(int ch) {
+
     double r,a,b,h;
+
     switch(ch) {
+
     case 1:
+
         cout<<"Enter the radius : "<<endl;
+
         cin>>r;
-        areaCircle(r);
+        if(check_for_positive(r)){
+            cout << "Cannot find area for zero and negative." << endl;
+        }else{
+
+            areaCircle(r);
+        }
+
         break;
+
     case 2:
+
         cout<<"Enter a side of the square : "<<endl;
+
         cin>>a;
-        areaSquare(a);
+        if(check_for_positive(a)){
+            cout << "Cannot find area for zero and negative." << endl;
+        }else{
+
+            areaSquare(a);
+        }    
+
         break;
+
     case 3:
-        cout<<"Enter the width and height of the rectangle : "<<endl;
-        cin>>a>>b;
-        areaRectangle(a,b);
+
+        cout<<"Enter the width of Rectangle: ";
+        cin >> a;
+        cout<<"Enter the height of Rectangle: ";
+        cin >> b;
+        if(check_for_positive(a)||check_for_positive(b)){
+            cout << "Cannot find area for zero and negative." << endl;
+        }else{
+
+            areaRectangle(a,b);
+        }    
+
         break;
+
     case 4:
-        cout<<"Enter the base and height of the triangle : "<<endl;
-        cin>>a>>h;
-        areaTriangle(a,h);
+
+        cout<<"Enter the base of the triangle : ";
+
+        cin>>a;
+        cout<<"Enter the height of triangle: ";
+        cin >> h;
+        if(check_for_positive(a)||check_for_positive(h)){
+            cout << "Cannot find area for zero and negative." << endl;
+        }else{
+
+            areaTriangle(a,h);
+        }
+
         break;
+
     default:
+
         cout<<"Wrong choice !"<<endl;
+
     }
+
 }
 
+
+
 double areaCircle(double r) {
+
     double result = PI *r *r;
+
     cout<<"The area of the circle is : "<<result<<endl;
+
     return result;
+
 }
 
+
+
 double areaSquare(double a) {
+
     double result = a* a;
+
     cout<<"The area of the Square is : "<<result<<endl;
+
     return result;
+
 }
 
+
+
 double areaRectangle(double a,double b) {
+
     double result = a* b;
+
     cout<<"The area of the Rectangle is : "<<result<<endl;
+
     return result;
+
 }
 
+
+
 double areaTriangle(double a,double h) {
+
     double result = (1/2.0)*a*h;
+
     cout<<"The area of the Triangle is : "<<result<<endl;
+
     return result;
+
+}
+
+bool check_for_positive(double numb){
+    if(numb==0||numb<0){
+        return true;
+    }
+    return false;
 }
 
+