From 8dfe3d339dc1542ee7bd59c000302765648e972c Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 29 Aug 2022 12:54:18 +0100
Subject: Generic solution for streaming collections that can be spanned

---
 lib/stream_support.cpp | 11 +++++++++++
 lib/stream_support.hpp | 18 ++++++++----------
 2 files changed, 19 insertions(+), 10 deletions(-)
 create mode 100644 lib/stream_support.cpp

diff --git a/lib/stream_support.cpp b/lib/stream_support.cpp
new file mode 100644
index 0000000..2054873
--- /dev/null
+++ b/lib/stream_support.cpp
@@ -0,0 +1,11 @@
+#include "stream_support.hpp"
+
+#include <array>
+#include <vector>
+
+static_assert(spanable<std::vector<int>>);
+// static_assert(spanable<std::vector<char>>);
+static_assert(spanable<std::array<int, 1>>);
+// static_assert(spanable<std::array<char, 1>>);
+static_assert(!spanable<std::string>);
+static_assert(!spanable<std::string_view>);
diff --git a/lib/stream_support.hpp b/lib/stream_support.hpp
index 0552b9d..3f0165c 100644
--- a/lib/stream_support.hpp
+++ b/lib/stream_support.hpp
@@ -5,6 +5,11 @@
 #include <maths.h>
 #include <span>
 #include <sstream>
+#include <type_traits>
+
+template<typename T>
+concept spanable = std::is_constructible_v<std::span<const typename T::value_type>, T> && !std::is_same_v<char,
+		std::decay_t<typename T::value_type>>;
 
 namespace std {
 	template<typename T, std::size_t L>
@@ -34,16 +39,9 @@ namespace std {
 		return (s << std::span {&v[0], L});
 	}
 
-	template<typename T, std::size_t L>
-	std::ostream &
-	operator<<(std::ostream & s, const array<T, L> & v)
-	{
-		return (s << std::span {v});
-	}
-
-	template<typename T>
+	template<spanable T>
 	std::ostream &
-	operator<<(std::ostream & s, const vector<T> & v)
+	operator<<(std::ostream & s, const T & v)
 	{
 		return (s << std::span {v});
 	}
@@ -61,7 +59,7 @@ streamed_string(const T & v)
 {
 	std::stringstream ss;
 	ss << v;
-	return ss.str();
+	return std::move(ss).str();
 }
 
 #define CLOG(x) std::cerr << #x " : " << x << "\n";
-- 
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