A comment about the erase-remove idiom.

ch11/ex11_3_4.cpp

@@ -17,10 +17,14 @@
 //! Exercise 11.4
 void word_count_pro(std::map<std::string, int> &m)
 {
-    for(std::string word; std::cin >> word; /* */)
+    std::string word;
+    while(std::cin >> word)
     {
-        for(auto& ch : word)    
+        for(auto& ch : word)
             ch = std::tolower(ch);
+        //! According to the erase-remove idiom.
+        //! For more information about the erase-remove idiom, please refer to
+        //! http://en.wikipedia.org/wiki/Erase-remove_idiom
         word.erase(std::remove_if(word.begin(), word.end(), ispunct), word.end());
         ++m[word];
     }
@@ -32,7 +36,8 @@ void word_count_pro(std::map<std::string, int> &m)
 void ex11_3()
 {
     std::map<std::string, std::size_t> word_count;
-    for(std::string word;   std::cin >> word;   /* */)
+    std::string word;
+    while(std::cin >> word)
     {
         ++word_count[word];
         for (const auto &elem : word_count)