added some comments for class Char, and added some TODO's

Char.cpp

@@ -10,11 +10,11 @@ Char& Char::operator=(char other)
 {
     auto data = new char[_string.size() + 2];   // space for new char & null-terminator
     std::strcpy(data, _string.c_str());
-    data[_index] = other;
+    data[_index] = other;                       // set the desired char
 
 
-    _string._str->operator--();
-    _string._str = new StringValue(data);
+    _string._str->operator--();                 // release old StringValue
+    _string._str = new StringValue(data);       // make a new one
 
     return *this;
 }

Char.h

@@ -5,6 +5,9 @@ class StringValue;
 
 
 
+// TODO: think about making ctors explict
+/* This class provides a simple wrapper for a char primitive, and implements
+ * copy-on-write semantics for the non-const String::operator[] via some magic */
 class Char
 {
 private:

String.h

@@ -6,6 +6,7 @@ class Char;
 
 
 
+// TODO: think about making ctors explict
 /* Design decisions:
  *              - Everything related to ref-counting is the responsibility of the StringValue class
  *              - Anything dynamically allocated is owned (and thus once deleted) by the StringValue class