Function stringify

src/framework/io/json.cpp:310–323

    const double value = as_number();
    if (!std::isfinite(value) || std::floor(value) != value) {
        throw std::runtime_error("json number is not an integer");
    }
    return static_cast<int64_t>(value);
}

float Value::as_f32() const {
    return static_cast<float>(as_number());
}

const std::string & Value::as_string() const {
    if (!is_string()) {
        throw std::runtime_error("json value is not a string");
    }
    return string_value_;
}

const Value::Array & Value::as_array() const {