I posted a question today and wanted to apply the tag to it, but such tag did not exist, and to create it I would need 300 reputation in this community.

Another user suggested that I gather a list of applicable questions and post them here as potential candidates for the tag (I don't expect the questions to be tagged as such, but rather to serve as an example of potential use of it).

I have managed to find five such questions easily (including the one I asked recently), but there are probably more questions regarding the topic out there and more that have yet to be asked.

The inclusion of the tag in this community seems plausible, as it is an important term related to programming and various software widely used in the industry.

Related tags that could also be considered (possibly as synonyms): and .

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    \$\begingroup\$ what is the exact difference between [lexical-analysis] and [lexer]? Isn't the use case of a [scanner]/[tokenizer] much more broad than that of a [lexer]? \$\endgroup\$
    – Vogel612
    Commented Jan 23, 2016 at 23:09
  • \$\begingroup\$ For mathematical expressions, we already have the more specific math-expression-eval, which I have now applied to two of the cited questions. \$\endgroup\$ Commented Jan 24, 2016 at 4:40
  • 4
    \$\begingroup\$ We also have parsing, compiler, and grammar. I'm reluctant to create a closely related tag in the subject cluster. Unless you can come up with clear guidelines about which tags apply to which questions, I'd rather not introduce [lexical-analysis]. \$\endgroup\$ Commented Jan 24, 2016 at 4:43
  • \$\begingroup\$ @rhino: Why is the tag "lexer" not sufficient. \$\endgroup\$ Commented Jan 27, 2016 at 21:12
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    \$\begingroup\$ @LokiAstari After giving it a second thought, the tag lexer could be better than lexical-analysis. Still, it seems the proposition was rejected altogether by 200_success with a list of alternative tags that are already in use. parsing and grammar seem to cover all the mentioned cases, and an appropriate tag was found in my case as well - math-expression-eval. Not sure whether this question remains valid. \$\endgroup\$
    – rhino
    Commented Jan 28, 2016 at 16:40
  • \$\begingroup\$ I created the tag @rhino. Do you mind creating a tag wiki for it? \$\endgroup\$
    – RubberDuck
    Commented Feb 3, 2016 at 14:45
  • \$\begingroup\$ @RubberDuck Thank you! As for the tag wiki, I don't feel like doing that - I took a glance at the wikis of some of the popular tags, and they all seem to be extensive descriptions with multiple external resources linked. I don't think my tag wiki would be just as elaborate, given that I'm not yet experienced with the topic. The relevant Wikipedia article introduced me to several related terms, but their definitions are not yet clear to me. I think it would be better to leave the task to someone else. \$\endgroup\$
    – rhino
    Commented Feb 3, 2016 at 16:54

1 Answer 1


I like this tag and think it's a good call.

  • is currently used for all kinds of things that are parsing, but not exactly lexical analysis. Having the tag gives us something to use for more formal definitions of parsing.

  • is very specifically tied to formal grammar definitions that are used as input to lexer/parser generators. It's related, but not necessarily appropriate for all lexical analysis questions.

  • is again, a related concept, but not quite right for all questions. A compiler uses output from a lexer & parser to translate the original input code into a different form. Compiling (and interpreting for that matter) is a distinctly different stage of the process from lexing.

I feel like this tag fills in a gap, and there are certainly at least a few questions that could use this tag.


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