From 138b84c1efd1e3e7b82ff1d9a19b45a905d5a031 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan.goodliffe@octal.co.uk>
Date: Fri, 18 Jan 2019 15:41:31 +0000
Subject: Literal operator based inline formatting

---
 libadhocutil/compileTimeFormatter.h                | 44 +++++++++++++++-------
 .../unittests/testCompileTimeFormatter.cpp         | 14 +++++++
 2 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/libadhocutil/compileTimeFormatter.h b/libadhocutil/compileTimeFormatter.h
index 5f0237e..6a932be 100644
--- a/libadhocutil/compileTimeFormatter.h
+++ b/libadhocutil/compileTimeFormatter.h
@@ -137,6 +137,11 @@ namespace AdHoc {
 				std::basic_stringstream<char_type> s;
 				return write(s, pn...).str();
 			}
+			template<typename ... Pn>
+			inline auto operator()(const Pn & ... pn) const
+			{
+				return get(pn...);
+			}
 
 			/**
 			 * Write the result of formatting to the given stream.
@@ -149,6 +154,11 @@ namespace AdHoc {
 			{
 				return Parser<stream, 0, Pn...>::run(s, pn...);
 			}
+			template<typename stream, typename ... Pn>
+			inline stream & operator()(stream & s, const Pn & ... pn) const
+			{
+				return write(s, pn...);
+			}
 
 		private:
 			template<typename stream, auto pos, typename ... Pn>
@@ -179,23 +189,31 @@ namespace AdHoc {
 				}
 			};
 	};
+
+	namespace literals {
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wgnu-string-literal-operator-template"
+#endif
+		template<typename T, T ... t> struct FMT
+		{
+			static constexpr char __FMT[] = {t...};
+		};
+		template<typename T, T ... t> inline auto operator""_fmt() noexcept
+		{
+			return AdHoc::Formatter<FMT<T, t...>::__FMT, sizeof...(t)>();
+		}
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+	}
 }
 
 #define AdHocFormatterTypedef(name, str, id) \
-	inline constexpr auto id = str; \
-	typedef ::AdHoc::Formatter<id> name
+    inline constexpr auto id = str; \
+    typedef ::AdHoc::Formatter<id> name
 #define AdHocFormatter(name, str) \
-	AdHocFormatterTypedef(name, str, MAKE_UNIQUE(name))
-
-// As far as I know, only clang/llvm version 5+ can compile this
-// so long as std=c++17
-#if __clang_major__ >= 5 && __cplusplus >= 201703
-#define scprintf(strmp, fmt, ...) \
-	([](decltype(strmp) & strm) -> auto & { \
-		static constexpr auto __FMT = fmt; \
-		return ::AdHoc::Formatter<__FMT>::write(strm, ##__VA_ARGS__); \
-	}(strmp))
-#endif
+    AdHocFormatterTypedef(name, str, MAKE_UNIQUE(name))
 
 #endif
 
diff --git a/libadhocutil/unittests/testCompileTimeFormatter.cpp b/libadhocutil/unittests/testCompileTimeFormatter.cpp
index 37d1947..65fbaa0 100644
--- a/libadhocutil/unittests/testCompileTimeFormatter.cpp
+++ b/libadhocutil/unittests/testCompileTimeFormatter.cpp
@@ -458,3 +458,17 @@ BOOST_AUTO_TEST_CASE(scprintf)
 }
 #endif
 
+using namespace AdHoc::literals;
+
+BOOST_AUTO_TEST_CASE(user_defined_literal_fmt_get)
+{
+	BOOST_CHECK_EQUAL("foo 42", "foo %?"_fmt(42));
+}
+
+BOOST_AUTO_TEST_CASE(user_defined_literal_fmt_write)
+{
+	std::stringstream str;
+	"foo %?"_fmt(str, 42);
+	BOOST_CHECK_EQUAL("foo 42", str.str());
+}
+
-- 
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