From 9875cfdc9821c44a5e9e49753d2bee34c8d7b299 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Mon, 25 Mar 2019 16:17:06 +0200
Subject: [PATCH] Add variant_npos and valueless_by_exception()

---
 include/boost/variant2/variant.hpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/boost/variant2/variant.hpp b/include/boost/variant2/variant.hpp
index 3cf2dc1..c109632 100644
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -1,7 +1,7 @@
 #ifndef BOOST_VARIANT2_VARIANT_HPP_INCLUDED
 #define BOOST_VARIANT2_VARIANT_HPP_INCLUDED
 
-// Copyright 2017, 2018 Peter Dimov.
+// Copyright 2017-2019 Peter Dimov.
 //
 // Distributed under the Boost Software License, Version 1.0.
 //
@@ -266,6 +266,10 @@ template<std::size_t I, class... T> struct variant_alternative<I, variant<T...>>
 
 #endif
 
+// variant_npos
+
+constexpr std::size_t variant_npos = -1;
+
 // holds_alternative
 
 template<class U, class... T> constexpr bool holds_alternative( variant<T...> const& v ) noexcept
@@ -1350,6 +1354,11 @@ public:
 
     // value status
 
+    constexpr bool valueless_by_exception() const noexcept
+    {
+        return false;
+    }
+
     using variant_base::index;
 
     // swap