From 44509498b703fa39668e42371e19f3f4ad7a5e82 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 28 Jan 2020 14:13:12 +1100
Subject: [PATCH] singleton: add a public query for validity

---
 singleton.hpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/singleton.hpp b/singleton.hpp
index a8b0361d..099651b2 100644
--- a/singleton.hpp
+++ b/singleton.hpp
@@ -27,6 +27,13 @@ namespace cruft {
         static SelfT *instance;
 
     public:
+        static bool
+        valid (void) noexcept
+        {
+            return instance;
+        }
+
+
         /// instantiates the one blessed value of this type.
         ///
         /// `instantiate` must be called once and once only before any calls