Thursday, December 20, 2012

Learn Vimscript the Hard Way, Commentary II

As I wrote in my first commentary on Steve Losh’s Learn Vimscript the Hard Way, I think it is a worthwhile book for people to read to get more familiar with the mechanics of customising their Vim environment.

What about those who want to use it to actually learn Vimscript?

It does an acceptable job of that too.

The chapters on Vimscript itself (19-27 and 35-40) cover the syntax and semantics of the language with examples and exercises spread throughout to give the learner necessary hands on experience.

I want to stress here that I feel Steve didn’t intend the what of those examples to be used literally in anyone’s vimrc files or personal plugins (in fact, I believe that to be true of the whole book at large) but rather the how of techniques shown. Don’t create your own little maps in your ~/.vimrc file for commenting lines in various filetypes and don’t write your own toy snippets system — very good plugins exist for these purposes already. Do learn that you can do these sorts of things so that when the time comes for you to really write something new, you will know how to.

Steve also provides two larger exercises starting respectively at chapters 32 and 41. The first is a new operator to grep for the motioned text, and the second is a full blown Plugin for a new programming language. Both serve as good models for the sort of larger works of the practising VimLer.

I do recommend this book because it’s freely available to read online. Another resource I would recommend for learning Vimscript is Damian Conway’s five part developerWorks article series, Scripting the Vim Editor — that’s how I first got into VimL (VimL is short for Vim Scripting Language and is another name for Vimscript). Vim’s built-in :help usr_41 is the user guide to writing Vim scripts and :help eval.txt is the reference manual on VimL’s expression evaluation.

Do you have a favourite resource for learning VimL?

Oops... I forgot to add my remarks on some of the technical aspects of Steve's work:

  • As Steve says, always use :help nore maps until you know you need otherwise.
  • In the same vein, always use :normal! (instead of the oft shown :normal) to avoid user-defined keymaps on the right hand side.
  • The :echom command (and friends) expects the evaluations of its expressions to be of type string. Use :help string( to coerce lists and dictionaries to strings for use in these commands. E.g.   :echom string(getline(1, '$'))
  • Vim's help system is context aware based on the format of the help tag. See :help help-context for the list of formats.

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