One of the most common features in a code editor is without doubt code completion (aka auto completion). Every programmer has seen this before and an explanation is no longer necessary. Still it makes sense to recall what *exactly* code completion is supposed to do. It should provide the programmer with a list of strings that can appear at a given position in the code (usually the one where the caret is). It is also sensible to require code to be syntactically correct up to the invocation point. Otherwise it is really difficult to predict what the user wanted to write actually.
Implementing code completion is a non-trivial task and there are different approaches possible. This posting describes a way to accomplish that with relatively few core code, as I have done it in MySQL Workbench. It delivers very precise results and requires only few changes to adjust it to different languages.