Saturday, February 13, 2010

Exploring Ctags: Motivations

I've been vaguely aware of Ctags for years, but only in the last few months have I gotten a handle on how it would benefit me. Part of the problem is that most mentions of Ctags seem to assume you already know the benefits: the Wikipedia entry does this, as does the Exuberant Ctags site. Worse, many discussions make it seem that it is just an auxiliary for vi-family editors, so perhaps not even relevant to those who, like me, haven't seriously used a vi derivative in years.

After seeing an explanation in the context of BBEdit, I have a much better idea of what Ctags provides. Essentially, it generates an index called a tags file that allows for easier code navigation across multiple files, in particular providing text completions and navigating to the definition of functions or other symbols. Within BBEdit, tags also are used to improve syntax highlighting.

I must admit that I find some of the praise for it to be overblown, but maybe I just need to try it. Of course, I don't use BBEdit, either. In fact, no editor that I regularly use supports Ctags. Let's do something about that. I'll work in the context of SubEthaEdit (SEE), since I have a fair amount of experience with scripting it, and of Exuberant Ctags, since it supports more languages than the Ctags built into Mac OS X.

I'll add two features to SEE, text completion and finding definitions. To some extent, these are redundant, in that SEE has text completions and a function pop-up, but they don't extend across multiple files in the same way as Ctags. I won't be able to do anything with syntax highlighting, as in BBEdit, but it should still be enough to try out Ctags.

Both features will be structured as AppleScripts invoking shell scripts to do most of the work. The AppleScripts both have a similar structure, consisting of:

  1. locating the tags file

  2. determining a search term to match against the tags file

  3. identifying and processing matching tags

  4. letting the user select from the matching tags

  5. doing something with the selection

I'll break these stages out into several posts.

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