Merge pull request #992 from cppalliance/more_format

Fix formatting support so that we can format into the middle of a string

Author: mborland

include/boost/decimal/fmt_format.hpp

@@ -77,7 +77,7 @@ constexpr auto parse_impl(ParseContext &ctx)
     }
 
     // If there is a . then we need to capture the precision argument
-    if (*it == '.')
+    if (it != ctx.end() && *it == '.')
     {
         ++it;
         ctx_precision = 0;
@@ -172,7 +172,6 @@ struct formatter
     template <typename FormatContext>
     auto format(const T& v, FormatContext& ctx) const
     {
-        auto out = ctx.out();
         std::array<char, 128> buffer {};
         auto buffer_front = buffer.data();
         bool has_sign {false};
@@ -229,7 +228,7 @@ struct formatter
             s.insert(s.begin() + static_cast<std::size_t>(has_sign), static_cast<std::size_t>(padding_digits) - s.size(), '0');
         }
 
-        return std::copy(s.begin(), s.end(), out);
+        return fmt::format_to(ctx.out(), "{}", s);
     }
 };
 

include/boost/decimal/format.hpp

@@ -77,7 +77,7 @@ constexpr auto parse_impl(ParseContext &ctx)
     }
 
     // If there is a . then we need to capture the precision argument
-    if (*it == '.')
+    if (it != ctx.end() && *it == '.')
     {
         ++it;
         ctx_precision = 0;
@@ -176,7 +176,6 @@ struct formatter<T>
         using namespace boost::decimal;
         using namespace boost::decimal::detail;
 
-        auto out = ctx.out();
         std::array<char, 128> buffer {};
         auto buffer_front = buffer.data();
         bool has_sign {false};
@@ -233,7 +232,7 @@ struct formatter<T>
             s.insert(s.begin() + static_cast<std::size_t>(has_sign), static_cast<std::size_t>(padding_digits) - s.size(), '0');
         }
 
-        return std::copy(s.begin(), s.end(), out);
+        return std::format_to(ctx.out(), "{}", s);
     }
 };
 

test/test_format.cpp

@@ -189,6 +189,13 @@ void test_hex()
     BOOST_TEST_EQ(std::format("{:A}", -std::numeric_limits<T>::signaling_NaN()), "-NAN(SNAN)");
 }
 
+template <typename T>
+void test_with_string()
+{
+    BOOST_TEST_EQ(std::format("Height is: {:.0f} meters", T {0}), "Height is: 0 meters");
+    BOOST_TEST_EQ(std::format("Height is: {} meters", T {2}), "Height is: 2 meters");
+}
+
 int main()
 {
     test_general<decimal32_t>();
@@ -219,6 +226,13 @@ int main()
     test_hex<decimal128_t>();
     test_hex<decimal_fast128_t>();
 
+    test_with_string<decimal32_t>();
+    test_with_string<decimal_fast32_t>();
+    test_with_string<decimal64_t>();
+    test_with_string<decimal_fast64_t>();
+    test_with_string<decimal128_t>();
+    test_with_string<decimal_fast128_t>();
+
     return boost::report_errors();
 }
 

test/test_format_fmtlib.cpp

@@ -213,6 +213,13 @@ void test_hex()
     BOOST_TEST_EQ(fmt::format("{:A}", -std::numeric_limits<T>::signaling_NaN()), "-NAN(SNAN)");
 }
 
+template <typename T>
+void test_with_string()
+{
+    BOOST_TEST_EQ(std::format("Height is: {:.0f} meters", T {0}), "Height is: 0 meters");
+    BOOST_TEST_EQ(std::format("Height is: {} meters", T {2}), "Height is: 2 meters");
+}
+
 #ifdef _MSC_VER
 #pragma warning(pop)
 #endif
@@ -247,6 +254,13 @@ int main()
     test_hex<decimal128_t>();
     test_hex<decimal_fast128_t>();
 
+    test_with_string<decimal32_t>();
+    test_with_string<decimal_fast32_t>();
+    test_with_string<decimal64_t>();
+    test_with_string<decimal_fast64_t>();
+    test_with_string<decimal128_t>();
+    test_with_string<decimal_fast128_t>();
+
     return boost::report_errors();
 }