From 14e1e7e7c16f1c8b41baa8e883d2364dd29490d6 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Sun, 26 May 2019 10:11:01 +1000
Subject: [PATCH] random: choose should return iterators/pointers

---
 random.hpp | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/random.hpp b/random.hpp
index 245df1ef..edcddda0 100644
--- a/random.hpp
+++ b/random.hpp
@@ -160,19 +160,30 @@ namespace cruft::random {
 
 
     ///////////////////////////////////////////////////////////////////////////
-    /// choose a value at random from an array
+    /// Choose a value at random from an array
+    ///
+    /// We return pointers (rather than values) so that we can return values
+    /// for empty containers without invalid dereferences.
+    ///
+    /// \return A pointer to the chosen value.
     template <typename T, size_t N>
-    T&
+    T*
     choose (T (&t)[N])
     {
         std::uniform_int_distribution<size_t> dist (0, N - 1);
-        return t[dist (generator ())];
+        return &t[dist (generator ())];
     }
 
 
-    //-------------------------------------------------------------------------
+    ///------------------------------------------------------------------------
+    /// Choose a value at random from a container.
+    ///
+    /// We return iterators (rather than values) so that we can return values
+    /// for empty containers without invalid dereferences.
+    //
+    /// \return An iterator to the chosen value.
     template <typename ContainerT, typename GeneratorT>
-    auto
+    typename ContainerT::iterator
     choose (ContainerT &data, GeneratorT &&gen)
     {
         if (data.empty ())
@@ -188,9 +199,15 @@ namespace cruft::random {
     }
 
 
-    //-------------------------------------------------------------------------
+    ///------------------------------------------------------------------------
+    /// Choose a value at random from a container.
+    ///
+    /// We return iterators (rather than values) so that we can return values
+    /// for empty containers without invalid dereferences.
+    ///
+    /// \return An iterator to the chosen value.
     template <typename ContainerT>
-    auto
+    typename ContainerT::iterator
     choose (ContainerT &data)
     {
         return choose (data, generator ());