From d98d1d057f19bdf3d8846b049da2e6d56e7c49ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philipp=20M=C3=B6ller?=
 <Philipp.Moeller@geometryfactory.com>
Date: Thu, 23 Jun 2011 13:09:49 +0000
Subject: [PATCH] Object: Made implicit conversion from optional<variant> safer
 Overload: Added generalised overloads and tests

---
 .gitattributes                                |  2 +
 STL_Extension/include/CGAL/Object.h           |  6 +--
 STL_Extension/include/CGAL/Overload.h         | 48 +++++++++++++++++++
 .../test/STL_Extension/test_Overload.cpp      | 43 +++++++++++++++++
 4 files changed, 96 insertions(+), 3 deletions(-)
 create mode 100644 STL_Extension/include/CGAL/Overload.h
 create mode 100644 STL_Extension/test/STL_Extension/test_Overload.cpp

diff --git a/.gitattributes b/.gitattributes
index ca70da0a47d..64ca2ffa2a9 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -3187,7 +3187,9 @@ Ridges_3/examples/Ridges_3/skip_vcproj_auto_generation -text
 Ridges_3/test/Ridges_3/data/ellipsoid.off -text svneol=unset#application/octet-stream
 Robustness/demo/Robustness/help/index.html svneol=native#text/html
 STL_Extension/doc_tex/STL_Extension/plusplus.png -text
+STL_Extension/include/CGAL/Overload.h -text
 STL_Extension/test/STL_Extension/test_Object.cpp -text
+STL_Extension/test/STL_Extension/test_Overload.cpp -text
 STL_Extension/test/STL_Extension/test_Uncertain.cpp -text
 STL_Extension/test/STL_Extension/test_type_traits.cpp -text
 Scripts/developer_scripts/autotest_cgal -text
diff --git a/STL_Extension/include/CGAL/Object.h b/STL_Extension/include/CGAL/Object.h
index 7cddf7ec320..ecad553ba40 100644
--- a/STL_Extension/include/CGAL/Object.h
+++ b/STL_Extension/include/CGAL/Object.h
@@ -107,9 +107,9 @@ class Object
     }
 #endif
 
-    // implicit constructor from boost::variant
-    template<typename T>
-    Object(const T& t) {
+    // implicit constructor from optionals containing variants
+    template<typename Variant>
+    Object(const boost::optional<Variant>& t) {
       // we cannot invoke another ctor from here, so we have to behave
       // like the copy ctor of our base
       if(t) {
diff --git a/STL_Extension/include/CGAL/Overload.h b/STL_Extension/include/CGAL/Overload.h
new file mode 100644
index 00000000000..d99ee0aebb1
--- /dev/null
+++ b/STL_Extension/include/CGAL/Overload.h
@@ -0,0 +1,48 @@
+#ifndef _COMPOSITE_VISITOR_H_
+#define _COMPOSITE_VISITOR_H_
+
+#include <CGAL/compiler_config.h>
+
+#if !defined(CGAL_CFG_NO_CPP0X_VARIADIC_TEMPLATES) && !defined(CGAL_CFG_NO_CPP0X_TUPLE)
+
+#include <tuple>
+
+namespace CGAL {
+
+template<typename T, std::size_t i, class U >
+struct overload_helper : public overload_helper<T, i - 1, U> {
+  typedef typename std::tuple_element<i - 1, T>::type inner_type;
+ 
+  typename inner_type::result_type operator()(typename inner_type::argument_type x) {
+    return std::get<i - 1>(static_cast<U*>(this)->t)(x); }
+ 
+  using overload_helper<T, i - 1, U>::operator();
+};
+ 
+template<typename T, class U>
+struct overload_helper<T, 1, U> {
+  typedef typename std::tuple_element<0 ,T>::type inner_type;
+ 
+  typename inner_type::result_type operator()(typename inner_type::argument_type x) {
+    return std::get<0>(static_cast<U*>(this)->t)(x); }
+};
+ 
+template<typename T>
+struct overload : public overload_helper<T, std::tuple_size<T>::value, overload<T> >
+{
+  // 
+  typedef typename std::tuple_element<0, T>::type::result_type result_type;
+
+  T t;
+  overload(T&& t) : t(t) {}
+  overload(const T& t) : t(t) {}
+};
+
+template<typename T>
+overload<T> make_overload(T&& t) { return overload<T>(t); }
+
+} // namespace CGAL
+#endif // !defined(CGAL_CFG_NO_CPP0X_VARIADIC_TEMPLATES) && !defined(CGAL_CFG_NO_CPP0X_TUPLE)
+
+#endif /* _COMPOSITE_VISITOR_H_ */
+
diff --git a/STL_Extension/test/STL_Extension/test_Overload.cpp b/STL_Extension/test/STL_Extension/test_Overload.cpp
new file mode 100644
index 00000000000..8d3cbef8009
--- /dev/null
+++ b/STL_Extension/test/STL_Extension/test_Overload.cpp
@@ -0,0 +1,43 @@
+#include <CGAL/compiler_config.h>
+
+#if !defined(CGAL_CFG_NO_CPP0X_VARIADIC_TEMPLATES) && !defined(CGAL_CFG_NO_CPP0X_TUPLE)
+
+#include <iostream>
+#include <tuple>
+#include <functional>
+#include <CGAL/Overload.h>
+#include <CGAL/assertions.h>
+#include <boost/variant.hpp>
+
+
+void test_overload() {
+  using namespace CGAL;
+  using std::function;
+
+  // basic overload checking
+  auto o = make_overload(std::make_tuple(
+                           function<int(int)>([](int) {  return 1; }),
+                           function<int(char)>([](char) {  return 2; }), 
+                           function<int(double)>([](double) { return 3; })));
+
+  CGAL_assertion(o(1) == 1);
+  CGAL_assertion(o('a') == 2);
+  CGAL_assertion(o(2.0) == 3);
+
+  // check for variants
+  boost::variant<int, char, double> v1 = 1;
+  boost::variant<int, char, double> v2 = 'a';
+  boost::variant<int, char, double> v3 = 2.0;
+
+  CGAL_assertion(boost::apply_visitor(o, v1) == 1);
+  CGAL_assertion(boost::apply_visitor(o, v2) == 2);
+  CGAL_assertion(boost::apply_visitor(o, v3) == 3);
+}
+
+#endif
+
+int main() {
+#if !defined(CGAL_CFG_NO_CPP0X_VARIADIC_TEMPLATES) && !defined(CGAL_CFG_NO_CPP0X_TUPLE)
+  test_overload();
+#endif
+}