|
◆ operator== [1/3]
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 T, typename SFINAE=void > class JSONSerializer = adl_serializer>
Compares two JSON values for equality according to the following rules:
- Two JSON values are equal if (1) they are from the same type and (2) their stored values are the same according to their respective
operator== .
- Integer and floating-point numbers are automatically converted before comparison. Note than two NaN values are always treated as unequal.
- Two JSON null values are equal.
- Note
- Floating-point inside JSON values numbers are compared with
json::number_float_t::operator== which is double::operator== by default. To compare floating-point while respecting an epsilon, an alternative comparison function could be used, for instance template<typename T, typename = typename std::enable_if<std::is_floating_point<T>::value, T>::type> inline bool is_same(T a, T b, T epsilon = std::numeric_limits<T>::epsilon()) noexcept { return std::abs(a - b) <= epsilon; }
-
NaN values never compare equal to themselves or to other NaN values.
- Parameters
-
[in] | lhs | first JSON value to consider |
[in] | rhs | second JSON value to consider |
- Returns
- whether the values lhs and rhs are equal
- Exception safety^^ No-throw guarantee: this function never throws exceptions.
- Complexity^^ Linear.
- Example^^ The example demonstrates comparing several JSON
- types. ^^
2 #include <nlohmann/json.hpp> 9 json array_1 = {1, 2, 3}; 10 json array_2 = {1, 2, 4}; 11 json object_1 = {{ "A", "a"}, { "B", "b"}}; 12 json object_2 = {{ "B", "b"}, { "A", "a"}}; 14 json number_2 = 17.000000000000001L; 15 json string_1 = "foo"; 16 json string_2 = "bar"; 19 std::cout << std::boolalpha; 20 std::cout << array_1 << " == " << array_2 << " " << (array_1 == array_2) << '\n'; 21 std::cout << object_1 << " == " << object_2 << " " << (object_1 == object_2) << '\n'; 22 std::cout << number_1 << " == " << number_2 << " " << (number_1 == number_2) << '\n'; 23 std::cout << string_1 << " == " << string_2 << " " << (string_1 == string_2) << '\n'; basic_json<> json default JSON class
Output (play with this example online):^^ [1,2,3] == [1,2,4] false
{"A":"a","B":"b"} == {"A":"a","B":"b"} true
17 == 17.0 true
"foo" == "bar" false
^^ The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/operator__equal.cpp -o operator__equal
- Since
- version 1.0.0
Definition at line 17918 of file json.hpp.
|