Exit Zen
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to a {std_ostream}.
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Initializer lists can be used to unambiguously construct or assign an <<ref_object>> or <<ref_array>>:
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An empty object may be constructed without incurring any memory allocations using the <<default_memory_resource,default memory resource>>. A <<ref_storage_ptr>> can also be explicitly specified:
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The opposite is also true: if there's a `tag_invoke` overload intended for <<ref_try_value_to>>, but not for <<ref_value_to>>, then calling <<ref_value_to>> will invoke the non-throwing overload, then construct a {ref_system_error} from the {ref_error_code} and throw it. Due to these fallbacks, it is recommended that users provide the overload from this section, rather then the other one, if they ever intend to use <<ref_try_value_to>>.
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When an <<ref_array>> is formatted to a {std_ostream}, the result is a valid JSON. That is, the array will be output with square brackets and the comma separated list of values, as per the JSON specification.
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library uses the <<ref_storage_ptr>> allocator model, has the same interface on all C++ versions, and has an optimized class layout to keep the size of JSON values small. <<ref_string>> also implements an improved interface that replaces extraneous overloads with ones that use <<ref_string_view>>.
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Similarly, an initializer list for an <<ref_object>> is always interpreted as an <<ref_object>>. In such cases, the initializer list must be a list of key-value pairs. For example, the following code will not compile because `1` is not convertible to a string:
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To permit custom memory allocation strategies, these containers all allow construction with a <<ref_storage_ptr>> which is a smart pointer to a {ref_memory_resource}. The constructor signatures have the same ordering as their `std` equivalents which use {req_Allocator} parameters. Once a container is constructed its memory resource can never change. Here we create an array without performing any dynamic allocations:
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resource>>, which uses the standard C++ allocator, and is designed for general use including mutation of the document after it is parsed. The <<ref_stream_parser>> object is reused between trials, allowing temporary memory allocated by the implementation to persist and improve performance.
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The requirement for an initializer list to be interpreted as an <<ref_object>> or <<ref_array>> when initializing such an entity only applies to the outermost initializer list; subsequent nested elements will follow the usual ambiguity resolution rules.
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small buffer optimisation is guaranteed, which avoids allocating memory for
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<<ref_object>>, or <<ref_string>>.
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Boost.JSON container.
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small strings.
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template such as `value_to_tag<T>`) so that its http://eel.is/c++draft/basic.lookup.argdep#2[associated namespaces and entities] are examined when name lookup is performed.
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Similar to the `std` counterpart, elements may be accessed directly by their key with bounds checking using <<ref_object_at>>, or without bounds checking using <<ref_object_operator_lb_rb>> which creates a null element if the key does not already exist:
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In all cases, the <<ref_storage_ptr>> owned by an <<ref_object>>, <<ref_array>>, or <<ref_value>> constructed from an initializer list will be propagated to each element, recursively.
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With augmented interface, operations requiring an input string are implemented as a single overload with a parameter of type <<ref_string_view>>, and can accept most string-like objects. Objects such as null terminated character pointers, `std::string`, <<ref_string>>, subranges of strings, and objects convertible to <<ref_string_view>> can all be passed to these functions.
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A <<ref_value>> constructed from `nullptr` or default constructed represents a null JSON element:
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Up until now we have shown how values may be constructed from a memory resource pointer, where ownership is not transferred. In this case the caller is responsible for ensuring that the lifetime of the resource is extended for the life of the container. Sometimes you want the container to acquire shared ownership of the resource. This is accomplished with <<ref_make_shared_resource>>:
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