Added quotes for strings in ranges and tuple likes.

include/fmt/ranges.h

@@ -162,6 +162,33 @@ void for_each(Tuple &&tup, F &&f) {
   const auto indexes = get_indexes(tup);
   for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
 }
+
+template<typename Arg>
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&, 
+    typename std::enable_if<!is_like_std_string<typename  std::decay<Arg>::type>::value>::type* = nullptr) {
+  return add_space ? " {}" : "{}";
+}
+
+template<typename Arg>
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&, 
+    typename std::enable_if<is_like_std_string<typename  std::decay<Arg>::type>::value>::type* = nullptr) {
+  return add_space ? " \"{}\"" : "\"{}\"";
+}
+
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char*) {
+  return add_space ? " \"{}\"" : "\"{}\"";
+}
+FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t*) {
+    return add_space ? L" \"{}\"" : L"\"{}\"";
+}
+
+FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char) {
+    return add_space ? " '{}'" : "'{}'";
+}
+FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t) {
+    return add_space ? L" '{}'" : L"'{}'";
+}
+
 }  // namespace internal
 
 template <typename T>
@@ -185,11 +212,7 @@ private:
         }
         internal::copy(formatting.delimiter, out);
       }
-      if (formatting.add_delimiter_spaces && i > 0) {
-        format_to(out, " {}", v);
-      } else {
-        format_to(out, "{}", v);
-      }
+      format_to(out, internal::format_str_quoted((formatting.add_delimiter_spaces && i > 0), v), v);
       ++i;
     }
 
@@ -252,11 +275,7 @@ struct formatter<RangeT, Char,
         }
         internal::copy(formatting.delimiter, out);
       }
-      if (formatting.add_delimiter_spaces && i > 0) {
-        format_to(out, " {}", *it);
-      } else {
-        format_to(out, "{}", *it);
-      }
+      format_to(out, internal::format_str_quoted((formatting.add_delimiter_spaces && i > 0), *it), *it);
       if (++i > formatting.range_length_limit) {
         format_to(out, " ... <other elements>");
         break;

test/ranges-test.cc

@@ -32,7 +32,7 @@ TEST(RangesTest, FormatVector2) {
 
 TEST(RangesTest, FormatMap) {
   std::map<std::string, int32_t> simap{{"one", 1}, {"two", 2}};
-  EXPECT_EQ("{(one, 1), (two, 2)}", fmt::format("{}", simap));
+  EXPECT_EQ("{(\"one\", 1), (\"two\", 2)}", fmt::format("{}", simap));
 }
 
 TEST(RangesTest, FormatPair) {
@@ -41,9 +41,9 @@ TEST(RangesTest, FormatPair) {
 }
 
 TEST(RangesTest, FormatTuple) {
-  std::tuple<int64_t, float, std::string> tu1{42, 3.14159265358979f,
-                                              "this is tuple"};
-  EXPECT_EQ("(42, 3.14159, this is tuple)", fmt::format("{}", tu1));
+  std::tuple<int64_t, float, std::string, char> tu1{42, 3.14159265358979f,
+                                              "this is tuple", 'i'};
+  EXPECT_EQ("(42, 3.14159, \"this is tuple\", 'i')", fmt::format("{}", tu1));
 }
 
 /// Check if  'if constexpr' is supported.
@@ -81,7 +81,7 @@ struct tuple_element<N, my_struct> {
 
 TEST(RangesTest, FormatStruct) {
   my_struct mst{13, "my struct"};
-  EXPECT_EQ("(13, my struct)", fmt::format("{}", mst));
+  EXPECT_EQ("(13, \"my struct\")", fmt::format("{}", mst));
 }
 
 #endif  // (__cplusplus > 201402L) || (defined(_MSVC_LANG) && _MSVC_LANG >