json/api/macros/json_has_ranges/index.md

JSON_HAS_RANGES

#define JSON_HAS_RANGES /* value */

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.

Default definition

The default value is detected based on the preprocessor macro __cpp_lib_ranges.

When the macro is not defined, the library will define it to its default value.

Known compiler/stdlib exclusions

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:

• GCC 11.1.0 — disabled (the shipped <ranges> header has a syntax error; issue #4440)
• libstdc++ < 11 — disabled (incomplete C++20 ranges support; issue #4440)
• Clang < 16 with libstdc++ — disabled (incomplete ranges support; issue #5161)
• libc++ < 160000 — disabled (incomplete C++20 ranges support; issue #4440)
• nvcc (CUDA) 12.0.x and 12.1.x — disabled (the enable_borrowed_range variable-template syntax triggers a parse error under these two toolkit versions; fixed in CUDA 12.2; issue #3907)

If JSON_HAS_RANGES is 0 despite __cpp_lib_ranges being defined, one of the exclusions above likely applies to your toolchain.

Examples

Example

The code below forces the library to enable support for ranges:

#define JSON_HAS_RANGES 1
#include <nlohmann/json.hpp>

...

See also

• JSON_HAS_CPP_11 / JSON_HAS_CPP_14 / JSON_HAS_CPP_17 / JSON_HAS_CPP_20 / JSON_HAS_CPP_23 / JSON_HAS_CPP_26 - set supported C++ standard
• JSON_HAS_RANGE_VIEW_CONVERSION - control construction from std::ranges views
• JSON_HAS_STD_FORMAT - a similar feature-detection macro, for std::format/std::formatter support
• Supported Macros - guide to all supported macros

Version history

• Added in version 3.11.0.
• Added the exclusions for libstdc++ < 11, Clang < 16 with libstdc++, libc++ < 16, and nvcc (CUDA) 12.0.x and 12.1.x in version 3.13.0 unreleased. Before, only GCC 11.1.0 was excluded.