feat: floating point precision

include/common/utils.hpp

@@ -2,6 +2,9 @@
 
 #pragma once
 
+#include <iomanip>
+#include <limits>
+#include <sstream>
 #include <string>
 #include <type_traits>
 
@@ -233,6 +236,21 @@ inline constexpr string_t null_string()
 template <typename string_t, typename any_t>
 inline string_t to_basic_string(any_t&& arg)
 {
+#ifdef MEOJSON_KEEP_FLOATING_PRECISION
+    using real_type = std::remove_reference_t<any_t>;
+    if constexpr (std::is_floating_point_v<real_type>) {
+        if constexpr (std::is_same_v<string_t, std::string>) {
+            std::ostringstream oss;
+            oss << std::setprecision(std::numeric_limits<real_type>::max_digits10) << arg;
+            return oss.str();
+        }
+        else if constexpr (std::is_same_v<string_t, std::wstring>) {
+            std::wostringstream oss;
+            oss << std::setprecision(std::numeric_limits<real_type>::max_digits10) << arg;
+            return oss.str();
+        }
+    }
+#endif
     if constexpr (std::is_same_v<string_t, std::string>) {
         return std::to_string(std::forward<any_t>(arg));
     }

test/main.cpp

@@ -2,6 +2,7 @@
 
 #include "include_test.h"
 #include "json5_test.h"
+#include "precision_test.h"
 #include "serializing_test.h"
 
 int main()
@@ -23,6 +24,9 @@ int main()
     std::cout << "\n*** json5_test ***\n" << std::endl;
     success &= test_json5();
 
+    std::cout << "\n*** precision_test ***\n" << std::endl;
+    success &= precision_test();
+
     if (!success) {
         std::cout << "\n****** Test failed ******\n" << std::endl;
         return -1;

test/precision_test.cpp

@@ -0,0 +1,18 @@
+#define MEOJSON_KEEP_FLOATING_PRECISION
+
+#include "../include/json.hpp"
+
+#include <iomanip>
+#include <iostream>
+
+bool precision_test()
+{
+    double value = 3.141592653589793;
+    json::object obj_old = json::object { { "double", value } };
+    std::string obj_str = obj_old.to_string();
+    std::cout << obj_str << std::endl;
+    json::object obj_new = json::parse(obj_str).value().as_object();
+    std::cout << "old:" << std::hexfloat << value << std::endl;
+    std::cout << "new:" << std::hexfloat << obj_new.at("double").as_double() << std::endl;
+    return obj_new.at("double").as_double() == value;
+}

test/precision_test.h

@@ -0,0 +1,3 @@
+#pragma once
+
+extern bool precision_test();