JSON for Modern C++  2.0.3

§ basic_json() [17/23]

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 = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
template<typename CompatibleNumberFloatType , typename = typename std::enable_if< std::is_constructible<number_float_t, CompatibleNumberFloatType>::value and std::is_floating_point<CompatibleNumberFloatType>::value>::type>
nlohmann::basic_json::basic_json ( const CompatibleNumberFloatType  val)
inlinenoexcept

Create an floating-point number JSON value with a given content. This constructor allows any type CompatibleNumberFloatType that can be used to construct values of type number_float_t.

Template Parameters
CompatibleNumberFloatTypeA floating-point type which is compatible to number_float_t. Examples may include the types float or double.
Parameters
[in]vala floating-point to create a JSON number from
Note
RFC 7159, 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 val is not a number, a JSON null value is created instead.
Complexity
Constant.
Example
The example below shows the construction of several floating-point number values from compatible types.
1 #include <json.hpp>
2 
3 using json = nlohmann::json;
4 
5 int main()
6 {
7  // create values of different floating-point types
8  float f42 = 42.23;
9  float f_nan = 1.0f / 0.0f;
10  double f23 = 23.42;
11 
12  // create JSON numbers
13  json j42(f42);
14  json j_nan(f_nan);
15  json j23(f23);
16 
17  // serialize the JSON numbers
18  std::cout << j42 << '\n';
19  std::cout << j_nan << '\n';
20  std::cout << j23 << '\n';
21 }
basic_json<> json
default JSON class
Definition: json.hpp:10122
Output (play with this example online):
42.2299995422363
null
23.42
The example code above can be translated with
g++ -std=c++11 -Isrc doc/examples/basic_json__CompatibleNumberFloatType.cpp -o basic_json__CompatibleNumberFloatType 
See also
basic_json(const number_float_t) – create a number value (floating-point)
Since
version 1.0.0

Definition at line 1558 of file json.hpp.