corrections adjustments motivated by first real review of the library

examples/example3.cpp

@@ -3,36 +3,44 @@
 #include <iostream>
 
 #include "../include/safe_integer.hpp"
-//#include "../include/safe_compare.hpp"
+#include "../include/safe_compare.hpp"
 
 void detected_msg(bool detected){
     std::cout << (detected ? "error detected!" : "error NOT detected! ") << std::endl;
 }
 
 int main(int argc, const char * argv[]){
-    std::cout << "example 3: ";
-    std::cout << "implicit conversions change data values" << std::endl;
+    std::cout << "example 3:";
+    std::cout << "undetected underflow in data type" << std::endl;
     std::cout << "Not using safe numerics" << std::endl;
     try{
-        int x = -1000;
+        unsigned int x = 0;
         // the following silently produces an incorrect result
-        char y = x;
+        --x;
+        // because C/C++ implicitly converts mis-matched arguments to int
+        // suggests that the operation is correct
+        assert(x == -1);
+        // even though it's not !!!
+
+        // however, safe_compare does detect the error
+        assert(! boost::numeric::safe_compare::equal(x, -1));
+        std::cout << x << " != " << -1;
         detected_msg(false);
     }
     catch(...){
         assert(false); // never arrive here
     }
-    // solution: replace int with safe<int> and char with safe<char>
+    // solution: replace unsigned int with safe<unsigned int>
     std::cout << "Using safe numerics" << std::endl;
     try{
         using namespace boost::numeric;
-        safe<int> x = -1000;
-        // throws exception when conversion change data value
-        safe<char> y = x;
+        safe<unsigned int> x = 0;
+        // decrement unsigned to less than zero throws exception
+        --x;
         assert(false); // never arrive here
     }
     catch(std::range_error & e){
-        std::cout << e.what() << std::endl;
+        std::cout << e.what();
         detected_msg(true);
     }
     return 0;