fixed #97

- added functions is_structured() and is_primitive()
- updated documentation
- updated test cases

doc/examples/operator__value_t.cpp

@@ -0,0 +1,34 @@
+#include <json.hpp>
+
+using namespace nlohmann;
+
+int main()
+{
+    // create JSON values
+    json j_null;
+    json j_boolean = true;
+    json j_number_integer = 17;
+    json j_number_float = 23.42;
+    json j_object = {{"one", 1}, {"two", 2}};
+    json j_array = {1, 2, 4, 8, 16};
+    json j_string = "Hello, world";
+
+    // call operator value_t()
+    json::value_t t_null = j_null;
+    json::value_t t_boolean = j_boolean;
+    json::value_t t_number_integer = j_number_integer;
+    json::value_t t_number_float = j_number_float;
+    json::value_t t_object = j_object;
+    json::value_t t_array = j_array;
+    json::value_t t_string = j_string;
+
+    // print types
+    std::cout << std::boolalpha;
+    std::cout << (t_null == json::value_t::null) << '\n';
+    std::cout << (t_boolean == json::value_t::boolean) << '\n';
+    std::cout << (t_number_integer == json::value_t::number_integer) << '\n';
+    std::cout << (t_number_float == json::value_t::number_float) << '\n';
+    std::cout << (t_object == json::value_t::object) << '\n';
+    std::cout << (t_array == json::value_t::array) << '\n';
+    std::cout << (t_string == json::value_t::string) << '\n';
+}