3 files changed, 35 insertions, 27 deletions
diff --git a/include/gsl/gsl_narrow b/include/gsl/gsl_narrow
new file mode 100644
index 0000000..be04f2d
--- /dev/null
+++ b/include/gsl/gsl_narrow
@@ -0,0 +1,33 @@
+
+#ifndef GSL_NARROW_H
+#define GSL_NARROW_H
+#include <gsl/gsl_assert> // for Expects
+#include <gsl/gsl_util> // for narrow_cast
+namespace gsl
+{
+struct narrowing_error : public std::exception
+{
+};
+
+// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
+template <class T, class U>
+GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
+GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
+constexpr
+T narrow(U u) noexcept(false)
+{
+    constexpr const bool is_different_signedness = (std::is_signed<T>::value != std::is_signed<U>::value);
+
+    const T t = narrow_cast<T>(u);
+
+    if (static_cast<U>(t) != u
+        || (is_different_signedness
+            && ((t < T{}) != (u < U{}))))
+    {
+        throw narrowing_error{};
+    }
+
+    return t;
+}
+}
+#endif // GSL_NARROW_H
+\ No newline at end of file
diff --git a/include/gsl/gsl_util b/include/gsl/gsl_util
index 89fb2ee..d771414 100644
--- a/include/gsl/gsl_util
+++ b/include/gsl/gsl_util
@@ -86,31 +86,6 @@ constexpr T narrow_cast(U&& u) noexcept
     return static_cast<T>(std::forward<U>(u));
 }
 
-struct narrowing_error : public std::exception
-{
-};
-
-// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
-template <class T, class U>
-GSL_SUPPRESS(type.1) // NO-FORMAT: attribute
-GSL_SUPPRESS(f.6) // NO-FORMAT: attribute // TODO: MSVC /analyze does not recognise noexcept(false)
-constexpr
-T narrow(U u) noexcept(false)
-{
-    constexpr const bool is_different_signedness = (std::is_signed<T>::value != std::is_signed<U>::value);
-    
-    const T t = narrow_cast<T>(u);
-    
-    if (static_cast<U>(t) != u
-        || (is_different_signedness
-            && ((t < T{}) != (u < U{}))))
-    {
-        throw narrowing_error{};
-    }
-    
-    return t;
-}
-
 //
 // at() - Bounds-checked way of accessing builtin arrays, std::array, std::vector
 //
diff --git a/tests/utils_tests.cpp b/tests/utils_tests.cpp
index ac83e2d..fae48f5 100644
--- a/tests/utils_tests.cpp
+++ b/tests/utils_tests.cpp
@@ -16,8 +16,8 @@
 
 #include <gtest/gtest.h>
 
-#include <gsl/gsl_util> // for narrow, finally, narrow_cast, narrowing_e...
-
+#include <gsl/gsl_util>     // finally, narrow_cast
+#include <gsl/gsl_narrow>   // for narrow, narrowing_error
 #include <algorithm>   // for move
 #include <functional>  // for reference_wrapper, _Bind_helper<>::type
 #include <limits>      // for numeric_limits