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Merge pull request #1984 from dota17/document-fix

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Modify the document about operator==
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Niels Lohmann 2020-04-11 18:55:18 +02:00 committed by GitHub
commit 4396a68d2d
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2 changed files with 36 additions and 5 deletions
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20
include/nlohmann/json.hpp
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@ -5632,13 +5632,13 @@ class basic_json
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.
comparison. Note that 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](https://github.com/mariokonrad/marnav/blob/master/src/marnav/math/floatingpoint.hpp#L34-#L39)
[comparison function](https://github.com/mariokonrad/marnav/blob/master/include/marnav/math/floatingpoint.hpp#L34-#L39)
could be used, for instance
@code {.cpp}
template<typename T, typename = typename std::enable_if<std::is_floating_point<T>::value, T>::type>
@ -5647,6 +5647,22 @@ class basic_json
return std::abs(a - b) <= epsilon;
}
@endcode
Or you can self-defined operator equal function like this:
@code {.cpp}
bool my_equal(const_reference lhs, const_reference rhs) {
const auto lhs_type lhs.type();
const auto rhs_type rhs.type();
if (lhs_type == rhs_type) {
switch(lhs_type)
// self_defined case
case value_t::number_float:
return std::abs(lhs - rhs) <= std::numeric_limits<float>::epsilon();
// other cases remain the same with the original
...
}
...
}
@endcode
@note NaN values never compare equal to themselves or to other NaN values.

21
single_include/nlohmann/json.hpp
View File

@ -20491,13 +20491,13 @@ class basic_json
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.
comparison. Note that 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](https://github.com/mariokonrad/marnav/blob/master/src/marnav/math/floatingpoint.hpp#L34-#L39)
[comparison function](https://github.com/mariokonrad/marnav/blob/master/include/marnav/math/floatingpoint.hpp#L34-#L39)
could be used, for instance
@code {.cpp}
template<typename T, typename = typename std::enable_if<std::is_floating_point<T>::value, T>::type>
@ -20506,7 +20506,22 @@ class basic_json
return std::abs(a - b) <= epsilon;
}
@endcode
Or you can self-defined operator equal function like this:
@code {.cpp}
bool my_equal(const_reference lhs, const_reference rhs) {
const auto lhs_type lhs.type();
const auto rhs_type rhs.type();
if (lhs_type == rhs_type) {
switch(lhs_type)
// self_defined case
case value_t::number_float:
return std::abs(lhs - rhs) <= std::numeric_limits<float>::epsilon();
// other cases remain the same with the original
...
}
...
}
@endcode
@note NaN values never compare equal to themselves or to other NaN values.
@param[in] lhs first JSON value to consider