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--- cplusplus:repetition_examples [2013/03/01 01:05] – created mithat
+++ cplusplus:repetition_examples [2019/02/11 17:49] – [Input validation] mithat
@@ Line 42: / Line 42: @@
 ===== Sentinel-controlled repetition =====
-<file c++ simple-sentinel.cpp>// This program calculates the squares of integers. The user
+<file c++ simple-sentinel.cpp>    // This program determines whether test scores are passing marks.
-// enters -999 when finished.
+    #include <iostream>
-#include <iostream>
+    using namespace std;
-using namespace std;
-int main()
+    int main()
-{
+    {
-    int num = 1;
+        const unsigned int PASSING_SCORE = 60;
+        int score;
-    cout << "Enter an integer and I will tell you its square. " << endl;
+        cout << "Enter a test scrore and I will tell you if it is a passing mark." << endl;
-    cout << "Enter -999 to quit: ";
+        cout << "Enter -1 to quit: ";
-    cin >> num;
+        cin >> score;
-    while (num != -999)
+        while (score != -1)
+        {
+            if (score >= PASSING_SCORE)
+            {
+                cout <<  score << ": PASS" << endl;
+            }
+            else
+            {
+                cout <<  score << ": FAIL" << endl;
+            }
+            cout << "Enter a test scrore and I will tell you if it is a passing mark." << endl;
+            cout << "Enter -1 to quit: ";
+            cin >> score;
+        }
+        return 0;
+    }
+</file>
+===== Input validation =====
+<file c++ simple-input-validation.cpp>    // Simple example of input validation.
+    #include <iostream>
+    using namespace std;
+    int main()
     {
-        cout << num <<" squared is " << num * num << "." << endl
+        const int LOWER_BOUND = 0;
-             << endl;
+        const int UPPER_BOUND = 100;
-        cout << "Enter an integer and I will tell you its square. " << endl;
+        int num;
-        cout << "Enter -999 to quit: ";
+        cout << "Enter a number between " << LOWER_BOUND
+             << " and " << UPPER_BOUND << ": ";
         cin >> num;
-    }
-    return 0;
+        // Fall through loop only if input is valid.
-}</file>
+        while (num < LOWER_BOUND || num > UPPER_BOUND)
+        {
+            cout << "Enter a number between " << LOWER_BOUND
+                 << " and " << UPPER_BOUND << ": ";
+            cin >> num;
+        }
+        cout << "Congratulations, you can follow directions." << endl;
+        return 0;
+    }
+</file>
 ===== for =====
-<file c++ simple-for.cpp>// This program counts to an upper limit
+<file c++ simple-for.cpp>// This program counts to an upper limit using a for structure.
-// using a for structure.
 #include <iostream>
 using namespace std;
@@ Line 109: / Line 145: @@
 }
 </file>
+===== break and continue =====
+<file c++ simple-break.cpp>// Print out a list of powers of 2.
+#include <iostream>
+#include <cmath>
+using namespace std;
+int main()
+{
+    const int UPPER_LIMIT = 100;
+    int num = 1;    // counter
+    char choice;    // used to get user input
+    while (num <= UPPER_LIMIT)
+    {
+        cout << "2 to the " << num << " power is " << pow(2, num) << endl;
+        cout << "Should I go on? [y/N]: ";
+        cin >> choice;
+        if (choice == 'N' || choice == 'n')
+            break;    // (try replacing with 'continue')
+        num++;
+    }
+    cout << "Goodbye!" << endl;
+    return 0;
+}
+</file>