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= Comparison to Other Libraries

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:icon_good: pass:q[[.green]##&#10004##] :icon_bad:  pass:q[[.red]##&#10008##]

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There exist many C++ JSON libraries, but two are particularly noteworthy for the purpose of comparison: https://rapidjson.org/[RapidJSON], https://nlohmann.github.io/json/[JSON for Modern {cpp}] (referred to herein as nlohmann's JSON, or nlohmann), and https://github.com/lemire/simdjson[SIMD JSON].

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Comparison to nlohmann JSON

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Value Type: https://github.com/nlohmann/json/blob/00cb98a3d170161711ab912ae6acefba31f29f75/include/nlohmann/json.hpp#L165[`nlohmann::basic_json`]

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This library adopts a "kitchen sink" approach. It contains a wealth of features, even those with niche uses. Its weakness is that the many template parameters, while allowing for configurability, inhibit the best possible optimizations. The consequence is that the library performs poorly. The ability to configure every aspect of the value type has the paradoxical effect of making it less suitable as a vocabulary type.

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{icon_bad} `basic_json` is a class template. Libraries must agree on the

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choices of template parameters to be interoperable.

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{icon_bad} Too much customization. We struggle to see a use case for making

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`BooleanType` anything other than `bool`.

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{icon_bad} Poor separation of concerns. The `basic_json` container

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declaration needlessly conflates parsing and serialization APIs.

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{icon_bad} Limited allocator support. Only stateless allocators are allowed,

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which rules out the most important type of allocator, a local arena-based implementation.

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{icon_bad} No incremental parsing, no incremental serialization.

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{icon_bad} Slow parsing and serialization performance.

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{icon_good} Full-featured, including JSON Pointer, CBOR, and others.

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Comparison to RapidJSON

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Value Type: https://github.com/Tencent/rapidjson/blob/bb5f966b9939d6cdfbac3462a0410e185099b3af/include/rapidjson/document.h#L608[`rapidjson::GenericValue`]

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{icon_bad} The value type is not regular. Assignment is destructive,