An example how to use NSLingusticTagger to add syntax highlighting to natural language English text. Currently it highlights nouns, personal names and organization names in a body of text but you can easily hack it to tag other parts of speech.
Run the app and then a text document is displayed. By default the app pre-loads Martin Luther King Jr's "I Have a Dream" speech. You can replace the contents by pasting plain text or typing it directly in the editor window; however file load/save functions are not implemented as these are not relevant to the example.
Click on Process to invoke NSLinguisticTagger and then the document will be replaced with a read-only view that contains the syntax-highlighted document. This is a WebView and you can copy the text within and paste it to other application while retaining its formatting. To return to the editable view, just click on Process again.
You'll want to look at TextDocument.m where most of the action takes place. To change what language parts are tagged, you'll want to modify the renderText method. There's a rather complete set of if statements commented out that encompasses a most of what NSLinguisticTagger is able to recognize out of English text. Just un-comment the tags that you want then build and run the app. I've left most of them commented out since the output looks too distracting when all of those tags are colorized.
Please see LICENSE.txt for the license. If you're doing anything interesting with this project, let me know at adib@cutecoder.org.