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, class BinaryType = std::vector<std::uint8_t>>

bool operator< ( const_reference  lhs, const_reference  rhs  )

friend

comparison: less than

Compares whether one JSON value lhs is less than another JSON value rhs according to the following rules:

• If lhs and rhs have the same type, the values are compared using the default < operator.
• Integer and floating-point numbers are automatically converted before comparison
• In case lhs and rhs have different types, the values are ignored and the order of the types is considered, see operator<(const value_t, const value_t).

Parameters

[in]	lhs	first JSON value to consider
[in]	rhs	second JSON value to consider

Returns

whether lhs is less than rhs

@complexity Linear.

@exceptionsafety No-throw guarantee: this function never throws exceptions.

@liveexample{The example demonstrates comparing several JSON types.,operator__less}

Since

version 1.0.0

Definition at line 24235 of file json.hpp.

    {
        const auto lhs_type = lhs.type();
        const auto rhs_type = rhs.type();
 
        if (lhs_type == rhs_type)
        {
            switch (lhs_type)
            {
                case value_t::array:
                    // note parentheses are necessary, see
                    // https://github.com/nlohmann/json/issues/1530
                    return (*lhs.m_value.array) < (*rhs.m_value.array);
 
                case value_t::object:
                    return (*lhs.m_value.object) < (*rhs.m_value.object);
 
                case value_t::null:
                    return false;
 
                case value_t::string:
                    return (*lhs.m_value.string) < (*rhs.m_value.string);
 
                case value_t::boolean:
                    return (lhs.m_value.boolean) < (rhs.m_value.boolean);
 
                case value_t::number_integer:
                    return (lhs.m_value.number_integer) < (rhs.m_value.number_integer);
 
                case value_t::number_unsigned:
                    return (lhs.m_value.number_unsigned) < (rhs.m_value.number_unsigned);
 
                case value_t::number_float:
                    return (lhs.m_value.number_float) < (rhs.m_value.number_float);
 
                case value_t::binary:
                    return (*lhs.m_value.binary) < (*rhs.m_value.binary);
 
                case value_t::discarded:
                default:
                    return false;
            }
        }
 
        else if (lhs_type == value_t::number_integer && rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_integer) < rhs.m_value.number_float;
        }
 
        else if (lhs_type == value_t::number_float && rhs_type == value_t::number_integer)
        {
            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_integer);
        }
 
        else if (lhs_type == value_t::number_unsigned && rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_float;
        }
 
        else if (lhs_type == value_t::number_float && rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_unsigned);
        }
 
        else if (lhs_type == value_t::number_integer && rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_integer < static_cast<number_integer_t>(rhs.m_value.number_unsigned);
        }
 
        else if (lhs_type == value_t::number_unsigned && rhs_type == value_t::number_integer)
        {
            return static_cast<number_integer_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_integer;
        }
 
        // We only reach this line if we cannot compare values. In that case,
        // we compare types. Note we have to call the operator explicitly,
        // because MSVC has problems otherwise.
        return operator<(lhs_type, rhs_type);
    }