1 files changed, 47 insertions, 0 deletions
diff --git a/chapter9/vertical.cxx b/chapter9/vertical.cxx
new file mode 100644
index 0000000..fc84e14
--- /dev/null
+++ b/chapter9/vertical.cxx
@@ -0,0 +1,47 @@
+// FILE: vertical.cxx
+// two recursive functions that write the digits of a number vertically.
+#include <iostream>  // Provides cin, cout
+#include <cstdlib>   // Provides EXIT_SUCCESS
+using namespace std;
+
+void write_vertical(unsigned int number);
+void super_write_vertical(int number);
+
+int main( ) {
+    int i;
+
+    cout << "Please type a non-negative number: ";
+    cin >> i;
+    cout << "The digits of that number are:" << endl;
+    write_vertical(i);
+
+    cout << "Please type a negative number: ";
+    cin >> i;
+    cout << "The digits of that number are:" << endl;
+    super_write_vertical(i);
+
+    cout << "Let's get vertical!" << endl;
+    return EXIT_SUCCESS;
+}
+void write_vertical(unsigned int number) {
+    if (number < 10)
+        cout << number << endl; // Write the one digit
+    else {
+        write_vertical(number/10);          // Write all but the last digit
+        cout << number % 10 << endl;        // Write the last digit
+    }
+}
+void super_write_vertical(int number) {
+    if (number < 0) {
+        cout << '-' << endl;                 // print a negative sign
+        super_write_vertical(abs(number));   // abs computes absolute value
+        // This is Spot #1 referred to in the text.
+    }
+    else if (number < 10)
+        cout << number << endl;              // Write the one digit
+    else {
+        super_write_vertical(number/10);     // Write all but the last digit
+        // This is Spot #2 referred to in the text.
+        cout << number % 10 << endl;         // Write the last digit
+    }
+}