Parsing simple zeroes throws type exception

[tksharpless]

Description

Not strictly a bug, but not ideal. Many apps print a simple '0' for all zero numbers, regardless of type. nlohmann-json parses those as unsigned int and throws an exception, for example in value(var, 0.0). There should be an option to promote 0 to float in this case; perhaps even for other numbers that look like an int. Or maybe there is such an option and I don't know it?

Reproduction steps

parse a Json file (not written by nlohmann, of course) that contains simple integer strings as values that you know should be float, using value(var, 0.0).

Expected vs. actual results

expect automatic promotion to double or whatever I assign the value to
get an exception complaining of incompatible types

Minimal code example

No response

Error messages

No response

Compiler and operating system

MSVCC 2022 Win10

Library version

3.9.1

Validation

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

[ProlificCoder17]

Hello I hope you're well, I am new but also very much ready to learn. I would like to help fix this bug

[arifghaz]

Hello, I have take some look at this issue and it seems to me that I can fix this by creating a special value function for integer/float. But, considering that this issue can potentially be handled by the user themselves during parsing, is there a need to implement the function to specifically caters for this one specific scenario.

[nlohmann]

@tksharpless @arifghaz I currently fail to reproduce the issue - I seem to not understand it. Here is a code example:

#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() {
	auto j = json::parse("{\"zero\": 0}"); // parse a 0, store it as unsigned int
	auto x = j.value("zero", 0.0);         // call the value function with 0.0 as default
}

Can you clarify?

[tksharpless]

Your test example fails to build with Microsoft C++ (via vsCode). The folder 'json' is the top level of a fresh clone of your GitHub project. Here is the console listing: cmd /c chcp 65001>nul && cl.exe /Zi /EHsc /nologo /IC:/Users/tksha/Projects/lohmann/json/include /FeC:\Users\tksha\Projects\lohmann\lohmann-zero.exe C:\Users\tksha\Projects\lohmann\lohmann-zero.cpp lohmann-zero.cpp C:\Users\tksha\Projects\lohmann\lohmann-zero.cpp(4): error C2653: 'json': is not a class or namespace name C:\Users\tksha\Projects\lohmann\lohmann-zero.cpp(4): error C3861: 'parse': identifier not found Build finished with error(s).

…

On Fri, Nov 29, 2024 at 11:29 AM Niels Lohmann ***@***.***> wrote: @tksharpless <https://github.com/tksharpless> @arifghaz <https://github.com/arifghaz> I currently fail to reproduce the issue - I seem to not understand it. Here is a code example: #include <nlohmann/json.hpp> using json = nlohmann::json; int main() { auto j = json::parse("{\"zero\": 0}"); // parse a 0, store it as unsigned int auto x = j.value("zero", 0.0); // call the value function with 0.0 as default } Can you clarify? — Reply to this email directly, view it on GitHub <#4253 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACBEZZVQQ5N2DZJDVADUQEL2DCI5VAVCNFSM6AAAAABSXL4TR2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMBYGEYTMNBVGI> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[nlohmann]

You need to set up the library search path to resolve <nlohmann/json.hpp>.

[tksharpless]

I did that. The compiler is seeing json.hpp.

…

On Sat, Nov 30, 2024 at 9:40 AM Niels Lohmann ***@***.***> wrote: You need to set up the library search path to resolve <nlohmann/json.hpp>. — Reply to this email directly, view it on GitHub <#4253 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACBEZZT6OFWH6FAYMTUJ5JT2DHE6BAVCNFSM6AAAAABSXL4TR2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMBYHE4DENJRG4> . You are receiving this because you were mentioned.Message ID: ***@***.***>