is_map_like

## `is_map_like`

Determine if `T` can be treated like a 1-to-1 mapping during conversions.

### Synopsis

Defined in header <boost/json/conversion.hpp>.

    template<
        class T>
    struct is_map_like;

### Description

Given `t`, a glvalue of type `T`, if

- `is_sequence_like<T>::value` is `true`; and

- given type `It` denoting `decltype(std::begin(t))`, and types `K` and `M`, `std::iterator_traits<It>::value_type` denotes `std::pair<K, M>`; and

- `std::is_string_like<K>::value` is `true`; and

- given `v`, a glvalue of type `V`, and `E`, the type denoted by `decltype(t.emplace(v))`, `std::is_tuple_like<E>::value` is `true`;

then the trait provides the member constant `value` that is equal to `true`. Otherwise, `value` is equal to `false`.

Users can specialize the trait for their own types if they don’t want them to be treated like mappings. For example:

    namespace boost {
    namespace json {

    template <>
    struct is_map_like<your::map> : std::false_type
    { };

    } // namespace boost
    } // namespace json

| The restriction for `t.emplace()` return type ensures that the container does not accept duplicate keys.

### Types Satisfying The Trait

`std::map`, `std::unordered_map`.

### See Also

`value_from`, `value_to`.

Convenience header <boost/json.hpp>.

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