Compile-time JSON example

json.cpp

constexpr auto jsv = R"({
    "feature-x-enabled": true,
    "value-of-y": 1729,
    "z-options": {
        "a": null,
        "b": "220 and 284",
        "c": [ 6, 28, 496 ]
    }
})"_json;

if constexpr (jsv["feature-x-enabled"]) {
    // code for feature x
} else {
    // code when feature x turned off
}