Update README.md

documenting the library

README.md

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 # stduuid
-A C++ cross-platform implementation for UUIDs.
+A C++ cross-platform implementation **for universally unique identifiers**, simply know as either UUID or GUID (mostly on Windows). A UUID is a 128-bit number used to uniquely identify information in computer systems, such as database table keys, COM interfaces, classes and type libraries, and many others.
+
+For information about UUID/GUIDs see:
+* [Universally unique identifier](https://en.wikipedia.org/wiki/Universally_unique_identifier)
+* [A Universally Unique IDentifier (UUID) URN Namespace](https://www.ietf.org/rfc/rfc4122.txt)
+
+## Library overview
+The library defines a namespace `uuids` with the following types and functions:
+* `uuid` is a class representing a UUID; this can be default constructed (a nil UUID), constructed from an array of bytes, or from a string.
+sentation (in lowercase)
+* `uuid_variant` is a strongly type enum representing the type of a UUID
+* `uuid_version` is a strongly type enum representing the version of a UUID
+* `make_uuid` is a parameterless function that creates a new UUID using the typical platform-specific method to create one (`CoCreateGuid` on Windows, `uuid_generate` on Linux, `CFUUIDCreate` on Mac).
+* `operator==` and `operator!=` for UUIDs comparison
+* `operator<<` to write a UUID to an output string using the standard repre
 
 This project is currently under development and should be ignored until further notice.
+
+## Using the library
+The following is a list of examples for using the library:
+* Creating a nil UUID
+```
+uuid empty;
+assert(empty.is_nil());
+assert(empty.size() == 16);
+```
+* Creating a new UUID
+```
+uuid const guid = uuids::make_uuid();
+assert(!guid.is_nil());
+assert(guid.size() == 16);
+assert(guid.version() == uuids::uuid_version::random_number_based);
+assert(guid.variant() == uuids::uuid_variant::rfc);
+```
+* Create a UUID from a string
+```
+using namespace std::string_literals;
+
+auto str = "47183823-2574-4bfd-b411-99ed177d3e43"s;
+uuid guid(str);
+assert(guid.string() == str);
+```
+or
+```
+auto str = L"47183823-2574-4bfd-b411-99ed177d3e43"s;
+uuid guid(str);
+assert(guid.wstring() == str);      
+```
+* Comparing UUIDS
+```
+uuid empty;
+uuid guid = uuids::make_uuid();
+
+assert(empty == empty);
+assert(guid == guid);
+assert(empty != guid);
+```
+* Swapping UUIDS
+```
+uuid empty;
+uuid guid = uuids::make_uuid();
+
+assert(empty.is_nil());
+assert(!guid.is_nil());
+
+std::swap(empty, guid);
+
+assert(!empty.is_nil());
+assert(guid.is_nil());
+
+empty.swap(guid);
+
+assert(empty.is_nil());
+assert(!guid.is_nil());
+```
+* Convert to string
+```
+uuid empty;
+assert(empty.string() == "00000000-0000-0000-0000-000000000000");
+assert(empty.wstring() == L"00000000-0000-0000-0000-000000000000");
+```