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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>
Returns the maximum number of elements a JSON value is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the JSON value.
- Returns
- The return value depends on the different types and is defined as follows:
Value type | return value |
null | 0 |
boolean | 1 |
string | 1 |
number | 1 |
object | result of function object_t::max_size() |
array | result of function array_t::max_size() |
- Complexity
- Constant, as long as array_t and object_t satisfy the Container concept; that is, their max_size() functions have constant complexity.
- Requirements
- This function satisfies the Container requirements:
- The complexity is constant.
- Has the semantics of returning
b.size() where b is the largest possible JSON value.
- Example
- The following code calls max_size on the different value types. Note the output is implementation specific.
10 json j_number_integer = 17;
11 json j_number_float = 23.42;
12 json j_object = {{ "one", 1}, { "two", 2}};
13 json j_array = {1, 2, 4, 8, 16};
14 json j_string = "Hello, world";
17 std::cout << j_null. max_size() << '\n';
18 std::cout << j_boolean. max_size() << '\n';
19 std::cout << j_number_integer. max_size() << '\n';
20 std::cout << j_number_float. max_size() << '\n';
21 std::cout << j_object. max_size() << '\n';
22 std::cout << j_array. max_size() << '\n';
23 std::cout << j_string. max_size() << '\n';
a class to store JSON values Definition: json.hpp:121
namespace for Niels Lohmann Definition: json.hpp:56
size_type max_size() const noexcept returns the maximum possible number of elements Definition: json.hpp:3022
Output: 0
1
1
1
256204778801521550
1152921504606846975
1
The example code above can be translated withg++ -std=c++11 -Isrc doc/examples/max_size.cpp -o max_size .
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