It can't support "nan", "inf", "-inf" for float type

[laok-solomon]

Description

when use PCL library, I need write some data to json.
my code is some like:

"write special float value to json file":
float userFilterValue = std::numeric_limits<float>::quiet_NaN();
nlohmann::ordered_json ser;
ser["userFilterValue“] = userFilterValue;
std::ofstream("test.json") << ser.dump(2);

"read special float value to json file":
float userFilterValue2 = 0;
nlohmann::ordered_json ser2;
std::ifstream("test.json") >> ser2;
userFilterValue2 = (float) ser["userFilterValue“];

I found that the "test.json" file data:

{
 "userFilterValue": null
}

Reproduction steps

I just want to serialize some special float value, such as "nan", "inf", "-inf"
but it throws exception wiht tips "type must be number, but is null"

Expected vs. actual results

when I write "nan", "inf" as float value, but it got "null"

Minimal code example

float userFilterValue = std::numeric_limits<float>::quiet_NaN();
nlohmann::ordered_json ser;
ser["userFilterValue“] = userFilterValue;
std::ofstream("test.json") << ser.dump(2);


nlohmann::ordered_json ser2;
std::ifstream("test.json") >> ser2;
float userFilterValue2 = (float) ser["userFilterValue“];

Error messages

type must be number, but is null

Compiler and operating system

visual studio 2019

Library version

3.10.4

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[nlohmann]

This is expected behavior, see https://json.nlohmann.me/features/types/number_handling/.

[laok-solomon]

thank you, I see now. I'm glad you gave me a reply.
Maybe, I need to use default value for special float variable when it read "null" value.
Avoiding this special float value to serialize to file or reading "null" float value from json file.

Thank you again for writing the JSON library, which is very concise and convenient.
Although boost.json library has come out, but I still think your json library is better.