beer_song: iteration 2

cpp/beer-song/beer_song.cpp

@@ -1,51 +1,57 @@
 #include "beer_song.h"
 
+#include <cassert>
 #include <cctype>
-#include <sstream>
 
 namespace beer {
 
 using namespace std;
 
+namespace {
+
+string count_bottles(int count)
+{
+    if (0 == count)
+        return "no more bottles";
+
+    if (1 == count)
+        return "1 bottle";
+
+    return to_string(count) + " bottles";
+};
+
+void capitalize_first(string &str)
+{
+    assert(!str.empty());
+    str.front() = toupper(str.front());
+};
+
+}
+
 string verse(int index)
 {
-    auto count_str = [](int count) -> string {
+    string result = count_bottles(index)
-
-        if (0 == count)
-            return "no more bottles";
-
-        if (1 == count)
-            return "1 bottle";
-
-        ostringstream oss;
-        oss << count << " bottles";
-
-        return oss.str();
-    };
-
-    auto capitalize_first = [](const string &str) -> string {
-
-        string result = str;
-        result.front() = toupper(result.front());
-        return result;
-    };
-
-    return capitalize_first(count_str(index))
         + " of beer on the wall, "
-        + count_str(index)
+        + count_bottles(index)
         + " of beer.\n"
         + (index ? string("Take ")
                     + (index == 1 ? "it" : "one")
                     + " down and pass it around, "
                  : string("Go to the store and buy some more, "))
-        + count_str(index ? index - 1 : 99)
+        + count_bottles(index ? index - 1 : 99)
         + " of beer on the wall.\n";
+
+    capitalize_first(result);
+
+    return result;
 }
 
 string sing(int from_index, int to_index)
 {
     string result;
 
+    assert(from_index >= to_index);
+
     for (int i = from_index; i >= to_index; --i) {
 
         result += (i == from_index ? "" : "\n");