REUSING-TAGS(7)        Miscellaneous Information Manual        REUSING-TAGS(7)

NAME
     reusing tags – beyond ctags

DESCRIPTION
     I've tried to start writing this post a couple times now and I keep
     getting bogged down in explanations, so I'm just going to tell you about
     some cool things I did and hope they make sense.

     When I wrote my first syntax highlighter, I decided that function
     definitions should have anchor links, because line number anchor links
     are entirely useless if you expect the file to change at all.  Since the
     syntax highlighter was somewhat deliberately just a big pile of regex, I
     hacked in more regex to try to identify function and type definitions.
     It wasn't elegant and it didn't always work well.  It did work though,
     and I found the links very useful.

     Recently I was thinking about the lexer generator lex(1) and decided to
     rewrite the syntax highlighter using it.  Really syntax highlighting is
     no different than lexical analysis.  I ran into a problem though, trying
     to preserve my anchor link function, because really that should involve
     some amount of parsing.  Trying to port my regex hacks to lex(1) made the
     lexers way more complicated and less reliable, so I gave up on it for a
     while.

     And then, probably in the shower, I realized I was approaching it
     completely from the wrong direction.  There's already a tool that does
     what I want, and I already use it: ctags(1).  All I need to do is use its
     output to insert anchor links into my syntax highlighter output.  In an
     afternoon I wrote htagml(1), which loads tag definitions for its input
     file, then scans through the input for where they match.  It can either
     HTML-escape the input as it goes, or use already formatted HTML being
     piped into it from a syntax highlighter.

     The result is three simple tools working together to accomplish what a
     more complex tool couldn't reliably achieve.  I'm very pleased with it,
     and I've updated my site and cgit to use the new lex(1)-based
     highlighter, ctags(1) and htagml(1).  I'm currently missing a lexer for
     sh(1), but I plan to write it eventually.  I also want to write a tool to
     generate tags for make(1), mdoc(7) and perhaps sh(1).  The cool thing
     about generating more kinds of tags is that they'll not only improve the
     HTML output, they'll also be usable in my editor.

     Speaking of generating different kinds of tags, I also wrote some scripts
     not too long ago for reading IETF RFCs offline.  The plain text files are
     available to rsync(1), but they're hard to navigate on their own.  By
     scanning the files for headings and generating tags, it allows jumping to
     sections using :ta or ^] in vi(1).  For nvim(1) I also added an :RFC
     command to open an RFC by number and set up ^] to work optimally for
     them.

     I'm still using vi(1) for most of my editing, by the way.  And of course
     ctags(1) was made to work with it!  Simple old tools are really doing it
     for me lately.

SEE ALSO
     htagml: https://causal.agency/bin/htagml.html
     hilex: https://causal.agency/bin/hilex.html
     rfctags: https://git.causal.agency/src/tree/doc/rfc

AUTHORS
     june <june@causal.agency>

ADDENDUM
     catgirl(1), pounce(1), litterbox(1) and scooper(1) all have new releases,
     if you're using any of them.  Also, this space is now available over
     gopher, if that's your sort of thing.

Causal Agency                  January 17, 2021                  Causal Agency