1 files changed, 44 insertions, 0 deletions
diff --git a/src/boost/libs/safe_numerics/example/example8.cpp b/src/boost/libs/safe_numerics/example/example8.cpp
new file mode 100644
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--- /dev/null
+++ b/src/boost/libs/safe_numerics/example/example8.cpp
@@ -0,0 +1,44 @@
+//  Copyright (c) 2018 Robert Ramey
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <iostream>
+
+#include <boost/safe_numerics/safe_integer.hpp>
+
+int main(int, const char *[]){
+    std::cout << "example 8:";
+    std::cout << "undetected erroneous expression evaluation" << std::endl;
+    std::cout << "Not using safe numerics" << std::endl;
+    try{
+        unsigned int x = 127;
+        unsigned int y = 2;
+        unsigned int z;
+        // this produces an invalid result !
+        z = y - x;
+        std::cout << "error NOT detected!" << std::endl;
+        std::cout << z << " != " << y << " - " << x << std::endl;
+    }
+    catch(const std::exception &){
+        std::cout << "error detected!" << std::endl;
+    }
+    // solution: replace int with safe<int>
+    std::cout << "Using safe numerics" << std::endl;
+    try{
+        using namespace boost::safe_numerics;
+        safe<unsigned int> x = 127;
+        safe<unsigned int> y = 2;
+        safe<unsigned int> z;
+        // rather than producing an invalid result an exception is thrown
+        z = y - x;
+        std::cout << "error NOT detected!" << std::endl;
+        std::cout << z << " != " << y << " - " << x << std::endl;
+    }
+    catch(const std::exception & e){
+        // which we can catch here
+        std::cout << "error detected:" << e.what() << std::endl;
+    }
+    return 0;
+}