fixed #125

ch09/ex9_32.cpp

@@ -1,16 +1,20 @@
 //
 //  ex9_32.cpp
-//  Exercise 9.32 
+//  Exercise 9.32
 //
 //  Created by pezy on 12/3/14.
 //  Copyright (c) 2014 pezy. All rights reserved.
 //
-//  @Brief  In the program onpage 354 would it be legal to write the call to insert as follows? 
+//  @Brief  In the program on page 354 would it be legal to write the call to insert as follows?
 //          If not, why not?
-//          iter = vi.insert(iter, *iter++); 
-//  @Answer - If only changed this, it's illegal obviously. like @Mooophy said:
-//          "*iter++  can result in deferencing an item out of range causing a runtime error."
-//          - If change "iter += 2;" to "++iter;" after the call. It is legal.(follow codes)
+//          iter = vi.insert(iter, *iter++);
+//  @Answer the statement is illegal, cause as said in Standard [5.2.2] :
+//          "The order of evaluation of arguments is unspecified."
+//          As a result, after entering function insert,
+//          iter could be its original value or original value + 1 or even anything else,
+//          depending on how compiler implemented.
+//          correct it as follows:
+//  @Discuss    https://github.com/Mooophy/Cpp-Primer/issues/125
 
 #include <iostream>
 #include <vector>
@@ -19,20 +23,18 @@ using std::vector; using std::cout; using std::endl;
 
 int main()
 {
-    vector<int> vi = {0,1,2,3,4,5,6,7,8,9}; 
-    auto iter = vi.begin(); 
-    while (iter != vi.end()) {    
-        if (*iter % 2) {        
-            iter = vi.insert(iter, *iter++);  
-            ++iter;
-        } else        
-            iter = vi.erase(iter); 
+    vector<int> vi = {0,1,2,3,4,5,6,7,8,9};
+    auto iter = vi.begin();
+    while (iter != vi.end()) {
+        if (*iter % 2) {
+            iter = vi.insert(iter, *iter);
+            iter += 2;
+        } else
+            iter = vi.erase(iter);
     }
-    
+
     for (auto i : vi)
         cout << i << " ";
-    
+
     return 0;
 }
-
-