From d096eb9d2155b8e678924566af1b841e6bc28f97 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 9 Feb 2022 12:51:02 +1000
Subject: [PATCH] tupe/value: add transform_array

---
 tuple/value.hpp | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/tuple/value.hpp b/tuple/value.hpp
index 424920ba..c037158b 100644
--- a/tuple/value.hpp
+++ b/tuple/value.hpp
@@ -245,4 +245,45 @@ namespace cruft::tuple::value {
             std::forward<TupleT> (val)
         );
     }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    namespace detail {
+        template <typename FunctionT, typename TupleT, size_t ...Index>
+        requires (
+            std::is_convertible_v<
+                std::tuple_element_t<Index, TupleT>,
+                std::common_type<
+                    std::tuple_element_t<Index, TupleT>...
+                >
+            > && ...
+        )
+        auto
+        transform_array (index::indices<Index...>, FunctionT &&func, TupleT &&val)
+        {
+            using value_type = std::common_type<
+                std::tuple_element_t<Index, TupleT>...
+            >;
+
+            return std::array<value_type, std::tuple_size_v<TupleT>> (
+                std::invoke (func, std::get<Index> (val))...
+            );
+        }
+    }
+
+
+    ///------------------------------------------------------------------------
+    /// Transform each element of a tuple with the supplied function and
+    /// return an array of the return values.
+    ///
+    /// The function must return types that have a computable common type.
+    template <typename FunctionT, typename TupleT>
+    auto
+    transform_array (FunctionT &&func, TupleT &&val)
+    {
+        return transform_array (
+            std::forward<FunctionT> (func),
+            std::forward<TupleT> (val)
+        );
+    }
 }