JSON for Modern C++  3.0
template<template< typename U, typename V, typename...Args > class ObjectType = std::map, template< typename U, typename...Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
nlohmann::basic_json::basic_json ( const number_float_t  value)
inline

Create a floating-point number JSON value with a given content.

Parameters
[in]valuea floating-point value to create a JSON number from
Note
RFC 7159 http://www.rfc-editor.org/rfc/rfc7159.txt, section 6 disallows NaN values:

Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

In case the parameter value is not a number, a JSON null value is created instead.
Complexity
Constant.
Example
The following example creates several floating-point values.
1 #include <json.hpp>
2 
3 using namespace nlohmann;
4 
5 int main()
6 {
7  // create values of different floating-point types
8  json::number_float_t v_ok = 3.141592653589793;
9  json::number_float_t v_nan = NAN;
10  json::number_float_t v_infinity = INFINITY;
11 
12  // create JSON numbers
13  json j_ok(v_ok);
14  json j_nan(v_nan);
15  json j_infinity(v_infinity);
16 
17  // serialize the JSON numbers
18  std::cout << j_ok << '\n';
19  std::cout << j_nan << '\n';
20  std::cout << j_infinity << '\n';
21 }
a class to store JSON values
Definition: json.hpp:130
namespace for Niels Lohmann
Definition: json.hpp:55
NumberFloatType number_float_t
a type for a number (floating-point)
Definition: json.hpp:495
Output (play with this example online):
3.14159265358979
null
null
The example code above can be translated with
g++ -std=c++11 -Isrc doc/examples/basic_json__number_float_t.cpp -o basic_json__number_float_t