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nlohmann
42 lines
1.5 KiB
Markdown
42 lines
1.5 KiB
Markdown
# JSON_HAS_RANGES
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```
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#define JSON_HAS_RANGES /* value */
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```
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This macro indicates whether the standard library has any support for ranges. Implies support for concepts. Possible values are `1` when supported or `0` when unsupported.
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## Default definition
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The default value is detected based on the preprocessor macro `__cpp_lib_ranges`.
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When the macro is not defined, the library will define it to its default value.
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Known compiler/stdlib exclusions
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Even when the feature-test macro `__cpp_lib_ranges` indicates ranges support is available, the library disables it on the following incomplete or broken toolchains:
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- **GCC 11.1.0** — disabled (the shipped `<ranges>` header has a syntax error; [issue #4440](https://github.com/nlohmann/json/issues/4440))
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- **libstdc++ < 11** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
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- **Clang < 16 with libstdc++** — disabled (incomplete ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
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- **libc++ < 160000** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
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If `JSON_HAS_RANGES` is `0` despite `__cpp_lib_ranges` being defined, one of the exclusions above likely applies to your toolchain.
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## Examples
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Example
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The code below forces the library to enable support for ranges:
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```
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#define JSON_HAS_RANGES 1
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#include <nlohmann/json.hpp>
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...
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```
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## Version history
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- Added in version 3.11.0.
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