By default, in vim (and most other editors)
- separate words. This means word/tag completion do not complete
eq:loc<c-x><c-]> but only
loc<c-x><c-]>. If there is no tag
loc..., nothing happens.
You can fix this by placing
However, this might have surprising side effects. For instance, if you have the equation
a-b:2, it is now treated as a single word.
The situation in latex is known to be complicated:
You can't get all LaTeX strings right using iskeyword, that is because the iskeyword works on characters and some characters may have different meanings in different contexts. (from iskeyword for latex)
Someone already asked the question iskeyword with context. But the answer is not affirmative to solve this issue.