From e02a4e259436e5db39249ed03cc80e6cf09fa16f Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 25 Jul 2023 10:00:30 +1000
Subject: [PATCH] hash/{std,tuple}: operators should be const

---
 hash/std.hpp   | 2 +-
 hash/tuple.hpp | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/hash/std.hpp b/hash/std.hpp
index 32239b4b..d250a770 100644
--- a/hash/std.hpp
+++ b/hash/std.hpp
@@ -12,7 +12,7 @@ namespace cruft::hash {
     // Useful as a component in more complex hash objects (eg, hash::tuple)
     struct std {
         template <typename ValueT>
-        auto operator () (ValueT &&val)
+        auto operator () (ValueT &&val) const
         {
             using inner_t = ::std::remove_cvref_t<ValueT>;
             return ::std::hash<inner_t> {} (::std::forward<ValueT> (val));
diff --git a/hash/tuple.hpp b/hash/tuple.hpp
index 1afe7700..8e7c47d5 100644
--- a/hash/tuple.hpp
+++ b/hash/tuple.hpp
@@ -19,7 +19,7 @@ namespace cruft::hash {
     public:
         template <typename ...ValueT>
         auto
-        operator() (std::tuple<ValueT...> const &val)
+        operator() (std::tuple<ValueT...> const &val) const
         {
             return compute (val, std::make_index_sequence<sizeof... (ValueT)> {});
         }
@@ -27,7 +27,7 @@ namespace cruft::hash {
     private:
         template <typename ...ValueT, std::size_t ...IndexV>
         auto
-        compute (std::tuple<ValueT...> const &val, std::index_sequence<IndexV...>)
+        compute (std::tuple<ValueT...> const &val, std::index_sequence<IndexV...>) const
         {
             return MixT {} (
                 ElementT {} (std::get<IndexV> (val))...