Question

As a programmer, I wonder if I could create my own package for LaTeX. I need something like that famous “listings” package, but something that is much more capable for my needs. I look for a listings solution that would watch out for a comment line like

// BEGIN LISTING 3122

// END LISTING 3122

No syntax highlighting, but intelligent support for tab indents. That package then would be used with a file name or path, walk through the lines and copy out just the snippets of interest.

I am 100% sure there is absolutely nothing like this on the market. So I want to program it for LaTeX. If that’s possible. I have no idea how and what programming language / IDE. Where would I start looking?

Answer 1

This is certainly possible, but it is non-trivial in the TeX programming language. I don’t have time to code it up at the moment but here’s an algorithm; I suggest asking on comp.text.tex for more specific LaTeX programming advice.

• Locally set all catcodes of special chars to “other” (\dospecials) and start reading in the input file line by line (\read)
• for each line compare the first however many tokens of the line (some iterative use of \if or \ifx; there might be a package to make this easier such as stringstrings or xstring)
  • in the default state throw away the input line and read the next
  • unless it’s // BEGIN LISTING, in which case save each line into a macro (something like \g@addto@macro)
  • until it’s // END LISTING, obviously
• keep going until the end of the file (\ifeof)

TeX by Topic is a good reference guide for this sort of work.