add enum example

manuals/meta_examples/enums_examples.cpp

@@ -8,8 +8,52 @@
 
 namespace
 {
+    enum class align {
+        left,
+        right,
+        center,
+    };
 }
 
-TEST_CASE("meta/meta_examples/enums") {
+TEST_CASE("meta/meta_examples/enums/type") {
     namespace meta = meta_hpp;
+
+    // 'align' enumeration type registration
+    meta::enum_<align>()
+        .evalue_("left", align::left)
+        .evalue_("right", align::right)
+        .evalue_("center", align::center);
+
+    // resolves a enumeration type by enumerator
+    const meta::enum_type align_type = meta::resolve_type(align::left);
+
+    // also, it can be resolved by static enumeration type
+    CHECK(align_type == meta::resolve_type<align>());
+
+    // allows to know the underlying type
+    CHECK(align_type.get_underlying_type() == meta::resolve_type<int>());
+
+    // prints all enumerators
+    fmt::print("* align:\n");
+    for ( auto&& [index, evalue] : align_type.get_evalues() ) {
+        fmt::print("  - {} = {}\n", index.name, evalue.get_underlying_value());
+    }
+}
+
+TEST_CASE("meta/meta_examples/enums/usage") {
+    namespace meta = meta_hpp;
+
+    const align e = align::center;
+
+    // resolves a enumeration type by enumerator instance 'e'
+    const meta::enum_type align_type = meta::resolve_type(e);
+
+    // converts the enumerator to its name
+    CHECK(align_type.value_to_name(e).value() == "center");
+
+    // also, it works with dynamic value types
+    CHECK(align_type.value_to_name(meta::value{e}).value() == "center");
+
+    // ... and back again
+    CHECK(align_type.name_to_value("center").value() == e);
 }