Merge pull request #14 from samchon/features/tuple

Add inverter from v3.1 to v2 and v3.

.gitignore

@@ -1,5 +1,5 @@
 bin/
-examples/normalized/
+examples/converted/
 lib/
 node_modules/
 

README.md

@@ -7,15 +7,15 @@
 [![Downloads](https://img.shields.io/npm/dm/@samchon/openapi.svg)](https://www.npmjs.com/package/@samchon/openapi)
 [![Build Status](https://github.com/samchon/openapi/workflows/build/badge.svg)](https://github.com/samchon/openapi/actions?query=workflow%3Abuild)
 
-OpenAPI definitions and converters for [typia](https://github.com/samchon/typia) and [nestia](https://github.com/samchon/nestia).
+OpenAPI definitions and converters (for [typia](https://github.com/samchon/typia) and [nestia](https://github.com/samchon/nestia)).
 
 `@samchon/openapi` is a collection of OpenAPI definitions of below versions. Those type definitions does not contain every properties of OpenAPI specification, but just have only some features essentially required for `typia` and `nestia` (especially [`@nestia/editor`](https://nestia.io/docs/editor/)).
 
   1. [Swagger v2.0](https://github.com/samchon/openapi/blob/master/src/SwaggerV2.ts)
   2. [OpenAPI v3.0](https://github.com/samchon/openapi/blob/master/src/OpenApiV3.ts)
   3. [OpenAPI v3.1](https://github.com/samchon/openapi/blob/master/src/OpenApiV3_1.ts)
 
-Also, `@samchon/openapi` provides emended OpenAPI v3.1 definition and its converter from above versions for convenient development. The keyword "emended" means that [`OpenApi`](https://github.com/samchon/openapi/blob/master/src/OpenApi.ts) is not a direct OpenAPI v3.1 specification (OpenApiV3_1), but a little bit shrinked to remove ambiguous and duplicated expressions of OpenAPI v3.1 for the convenience of typia and nestia
+Also, `@samchon/openapi` provides emended OpenAPI v3.1 definition and its converter/inverter from above versions for convenient development. The keyword "emended" means that [`OpenApi`](https://github.com/samchon/openapi/blob/master/src/OpenApi.ts) is not a direct OpenAPI v3.1 specification (OpenApiV3_1), but a little bit shrinked to remove ambiguous and duplicated expressions of OpenAPI v3.1 for the convenience of typia and nestia
 
 For example, when representing nullable type, OpenAPI v3.1 supports three ways. In that case, OpenApi remains only the third way, so that makes `typia` and `nestia` (especially [`@nestia/editor`](https://nestia.io/docs/editor/)) to be simple and easy to implement.
 
@@ -55,6 +55,14 @@ const input:
 
 // you can convert it to emended OpenAPI v3.1
 const output: OpenApi.IDocument = OpenApi.convert(input);
+
+// it is possible to downgrade to Swagger v2 or OpenAPI v3
+const v2: SwaggerV2 = OpenApi.downgrade(output, "2.0");
+const v3: OpenApiV3 = OpenApi.downgrade(output, "3.0");
+
+// you can utilize it like below
+OpenApi.downgrade(OpenApi.convert(v2), "3.0");
+OpenApi.downgrade(OpenApi.convert(v3), "2.0");
 ```