adding passing pointer by reference example and notes

labs/06_lists_iterators/README.md

@@ -95,5 +95,7 @@ and lists with one or two values. Also add a test or two of a node chain with so
 If you have time, write 2 versions of this function, one version should be iterative (using a for or while loop)
 and one version should be recursive.
 
+**Note**: this reverse function takes a pointer as its argument, but we are passing this pointer by reference, because we want to modify this pointer. To understand the concept of passing a pointer by reference, you are recommended to read and run this [example program](reference_to_a_pointer.cpp).
+
 **To complete this checkpoint**, show a TA or mentor your diagram and your debugged function(s) to
 reverse a homemade singly-linked list.

labs/06_lists_iterators/reference_to_a_pointer.cpp

@@ -0,0 +1,28 @@
+/* This example demonstrates the usage of passing a pointer by reference.
+ * It is needed when you want to modify the pointer.
+ */
+
+#include <iostream>
+
+// function to modify the value of a pointer through reference
+void modifyPointer(int* & ptr, int& newValue) {
+    ptr = &newValue;     // assign the address of newValue to the pointer
+}
+
+int main() {
+    int value = 42;
+    int* ptr = &value;
+
+    // print the original value of the pointer
+    std::cout << "Original value of pointer: " << *ptr << std::endl;
+
+    int newValue = 100;  // new value to assign to the pointer
+    // pass the pointer by reference to the function, so that we can change the pointer
+    modifyPointer(ptr, newValue);
+
+    // print the modified value of the pointer
+    std::cout << "Modified value of pointer: " << *ptr << std::endl;
+
+    return 0;
+}
+