Tuesday, August 27, 2013

Not Classy, VimLPOO!

Rise, fellow VimLers and cease sobbing onto your consoles about the stink of VimLPOO (VimL Programming Object Orientedly). Vim keeps an open mind and so should you.

tl;dr : VimL OOP can haz class-reopening like Ruby

Okay, maybe not exactly like Ruby, but check it:

VimL’s OOP is more like javascript’s than Ruby’s. It doesn’t have explicit classes. It uses dictionaries to store data and methods that operate on it.

Here is one way in VimL to create an object factory:

function! Kid(name)                  <1>
  let k = {}                         <2>
  let k.name = a:name                <3>
  func k.say(blah) dict              <4>
    echo self.name . ': ' . a:blah
  return k                           <5>

let boy = Kid('Jack')                <6>
let girl = Kid('Jill')
call boy.say('wassup?')              <7>
call girl.say('chillin'' at the hill. u?')
echo boy                             <8>
Jack: wassup?
Jill: chillin' at the hill. u?
{'name': 'Jack', 'say': function('69')}
  1. I like to use the full command form function when creating object factories (classes?).
  2. The object container is a dictionary (hash).
  3. You can explicitly set attributes outside of methods if desired.
  4. I like to use the short command form func for methods. The dict argument tells Vim that this is an instance method, providing us the self. accessor.
    Note You don’t need the ! on method declarations as you do for the outer-level.
  5. The factory must return the newly created object.
  6. Create an instance using the factory.
  7. Call methods using dot notation.
  8. The object in its native format is just a dictionary (hash).
Typically, after creating the object factory, the VimLPOO developer can’t re-open it to augment its behaviour although you can derive a new factory type from an existing one (inheritance without paternity):

function! RudeKid(name)
  let rk = Kid(a:name)               <1>
  func! rk.say(blah) dict            <2>
    echo self.name . ': Yo, biatch! ' . a:blah
  return rk

let boy = RudeKid('Jack')
let girl = Kid('Jill')
call boy.say('wassup?')
call girl.say('wtf?')
echo boy
Jack: Yo, biatch! wassup?
Jill: wtf?
{'name': 'Jack', 'say': function('72')}
  1. Base this object on the parent factory.
  2. Override methods as desired.
    Note The use of ! is now required because the method already exists in the base object.
But I’m not here today to talk about weak inheritance. I wanna play with class re-opening, Vim style.

As a quick recap, a Vim object is a dictionary with data and methods that can use the self. modifier internally to refer to its data and other methods. It turns out that Vim is not too particular about who gets to claim dict access on your objects. You’re free to create external functions, adorned with the dict modifier, and have them manipulate your objects as if they were created with the class originally:

function! s:slapped() dict
  echo self.name . " just got slapped!"

This happens to be a script-local (s:) function; global scope would work too, but why pollute unnecessarily? Now, if you tried to do a naive direct call of this, you’d be sorely disappointed:

call boy.slapped()
Error detected while processing jack_and_jill.vim:
Line   42:
E716: Key not present in Dictionary: slapped

That makes sense… We created slapped() as a script-local function, not a method on the boy instance.
Note Adding the method to the Kid() factory after having created the boy instance would be just as useless.

Happiness is just a call away:

call call('s:slapped', [], boy)

" Jack just got slapped!

:-D How cool is that?!

I have a little project in the works that uses this to allow clients of the engine to inject their own solutions to various parts of the workflow. It’s almost done, so I should be able to show something a bit more real-worldy soon. For now, what mischief can you concoct with this shiny new toy? I look forward to finding out. :-)

Vim on!

Monday, April 22, 2013

Sort Me A Column

Need to sort a column within your table without messing with the other columns?
Vim has your back with blockwise visual selections and a bit of gymnastics.

Sample table:
1 this 1 apple    is 1
2 this 4 durian   is 2
3 this 3 carrot   is 3
4 this 2 banana   is 4
5 this 5 eggplant is 5

Desired result:
1 this 1 apple    is 1
2 this 2 banana   is 2
3 this 3 carrot   is 3
4 this 4 durian   is 4
5 this 5 eggplant is 5

[wrong] Result of naive :sort command:
1 this 1 apple    is 1
2 this 4 durian   is 2
3 this 3 carrot   is 3
4 this 2 banana   is 4
5 this 5 eggplant is 5

[wrong] Result of :sort /^. / command (to skip leading numbers):
1 this 1 apple    is 1
4 this 2 banana   is 4
3 this 3 carrot   is 3
2 this 4 durian   is 2
5 this 5 eggplant is 5

A Solution

  1. Visually select the column of interest with ctrl-v
  2. Cut it with x
  3. Open a temporary scratch buffer with :enew
  4. Paste with p
  5. Sort with :sort
  6. If you need to, ensure your cursor is line 1, col 1 with gg0
  7. Visually select and yank everything, blockwisely with ctrl-vG$y
  8. Switch back to where you came from with ctrl-6 (ctrl-^)
  9. Jump to the start of your original cut with `[
  10. Paste with P

Saturday, April 20, 2013

Partial Explosion

Vim has a powerful regex spell, :help /\%[] . While it might look like the emoticon of a lunging crocodile, this little piece of regex lets vimmers match words in either their full form or any partial reduction thereof. That’s a messy explanation. A showing will help:

The pattern:


Will match: r, re, rea, and read

Unicorns, I know!

This actually gets a lot of love in Vim’s syntax highlighting file for its own language, VimL. I wish it didn’t to be honest. I actually deplore the availability of partial keyword forms like fu instead of the full form function. But that’s not why we’re here today, so let’s move on.

Not all regex engines support this awesome atom. In fact… I don’t know of any other that does.

I am in the process of creating a vim.lang file for source-highlighter. As you would expect, it has a regex based DSL for specifying syntax items. One such item is for keywords. Easy!, I thought, I’ll just grab the keywords from Vim’s syntax files and… oh, crap… It’s infested with \%[]

So… Let’s explode them.

With a quick regex, I got the Vim keywords split out onto separate lines, like this:


And then we can explode out the partial variations with this little regex:

:%s/^\(.\{-}\)\[\(.\{-}\)\]/\=join(map(range(len(submatch(2))+1),  'submatch(1).strpart(submatch(2), 0, v:val)'), ' ')/


arga argad argadd
ar arg args
bn bne bnex bnext
breaka breakad breakadd

And just in time for dinner, too.

I'd Tap That

The Ruby world and many others have a tap() method on a class way up in the hierarchy near God that lets the bug hunting developer peek inside of objects during execution to see what the gnomes are getting up to under the covers. I needed just such a tool for my latest dabblings in Vim, so I built one and thought I’d share it here:

function! Tap(thing)
  echom string(a:thing)
  return a:thing

It’s not very intimidating, I know, but thats a little gem of a function. I used it to debug the setting of the includeexpr option in Vim, as shown here:

set includeexpr=Tap(substitute(Tap(v:fname),'\\${\\?\\(\\w\\+\\)}\\?','\\=expand(\"$\".submatch(1))','g'))

I was suspicious that the v:fname variable was not being set properly before includeexpr was being evaluated by Vim. Tap() proved that to be the case which allowed me to focus my debug efforts on the real cause, instead of continuing to waste time fretting over the search and replace patterns in the substitute and whether I’d escaped them correctly or not. I only wish the Tap() inspiration had come to me sooner than it really did. Oh well… with Tap() as a permanent fixture in my ~/.vimrc, hopefully it won’t take me as long to think of it the next time I need its services.

Saturday, April 6, 2013



We've all been there before; all too often, in fact. There you are in the middle of a serious edit when all of a sudden some vile little gremlin spits at you from deep within Vim. "Argh!" You instantly seethe with indignant rage, vowing to righteously lance that festering pustule...! when the terrifying realisation strikes you - you don't know where this bug is coming from. "Gack." You say as you think to yourself: "It must be one of the plugins... surely? Ok... it could be in my ~/.vimrc... But no! I watered it only yesterday and there were hardly any weeds there. So, it's a plugin... But... which one? How am I supposed to find the menacing little urchin among all those other well behaving citizens in my plugin pool?" Historically the Vimmer faced with this situation has had very little option but to manually move plugins aside until the faulty one is found. This is a laborious, boring and very frustrating task. Even if you knew well enough to use binary search to speed up the process, it's still not something anyone wants to do. Thankfully now, you don't have to. Now, you can do it with Bisectly.

Bisectly is a plugin-manager agnostic fault localisation tool for finding which plugin is causing you nose-bleeds.

Bisectly uses BSFL (Binary Search Fault Localisation) to quickly whittle down the set of loaded plugins in search of the one causing you pain. It uses a cutesy command interface to identify which sessions the user considers fault-free (:Unicorns) or faulty (:Zombies). This process continues until a single plugin remains, which Bisectly considers to be the guilty party.

Plugin Manager Agnostic

Bisectly interrogates your normal Vim for its final set of &runtime paths before juggling those in the BSFL algorithm. As such, it should be completely independent of any plugin manager. I have tested it with pathogen only, but I don't foresee any issues with Vam or Vundle. Feedback appreciated on this.

Possible Futures

My original idea for the Zombies Vs Unicorns theme was actually in regard to using BSFL on locating faults within a user's ~/.vimrc file. I have a plugin that is all-but-finished for this purpose but it has been delayed until a better vimscript parser can be completed. Work on that is currently in progress.

I have dabbled with various solutions to this problem over the last year or so. Most of the other solutions were tied to pathogen or were broader, more generic endeavours (stretching beyond the realm of Vim). All of those solutions, though, utilised an automated testing framework to very rapidly locate the faulty component - in a matter of seconds. I had the idea for this incarnation of Bisectly today and rushed out the simpler manual code while it was fresh in my mind. However, I do intend to revisit this plugin to add support for an automated test framework.

Saturday, March 16, 2013

The Path of a Master VimLer

An apprentice approached a Master and said,
“Show me your best Vim.”
to which the Master responded,
“Everything in my Vim is best.
You cannot find here any piece of Vim that is not the best.”
At these words, the apprentice became enlightened.

What might the path to VimL mastery look like?
Here's what Raimondi & I think at the moment:

Trainee → Novice → Worker → Professional → Expert
  1. Trainee
    • Read the following parts of :help cmdline.txt
      • 3. Ex command-lines :help cmdline-lines
      • 4. Ex command-line ranges :help cmdline-ranges
      • 6. Ex special characters :help cmdline-special
    • Read the following parts of :help options.txt
      • 1. Setting options :help set-option
      • The following specific options:
        • :help 'debug'
        • :help 'eventignore'
        • :help 'ignorecase'
        • :help 'magic'
        • :help 'maxfuncdepth'
        • :help 'runtimepath'
        • :help 'verbose'
    • Read all of :help pattern.txt
    • Read the following parts of :help eval.txt
      • 1. Variables :help variables
      • 2. Expression syntax (skim) :help expression-syntax
      • 3. Internal variable :help internal-variables
      • 5. Defining functions :help user-functions
      • 7. Commands :help expression-commands
      • 9. Examples :help eval-examples
    • Read sections 41.1 - 41.8 in :help usr_41.txt
    • Read :help function-list (Vim’s built-in VimL library)
    • Read http://www.ibm.com/developerworks/linux/library/l-vim-script-1/index.html
    • Read http://learnvimscriptthehardway.stevelosh.com/
    • Pass the Trainee assessments
  2. Novice
    • Contribute bug fixes and small enhancements to existing plugins.
    • Read :help map.txt
      • Read :help 'timeout' option
      • Read :help 'maxmapdepth' option
    • Read :help usr_40.txt
    • Read :help autocmd.txt
    • Read :help filetype.txt
    • Read :help various.txt
      • In regard to :normal, read :help motion.txt
    • Pass the Novice assessments
  3. Worker
    • Read :help eval.txt
    • Read :help usr_41.txt
    • Create three or more plugins under the supervision of a Professional or Expert
    • Assist Novices
  4. Professional
    • Actively support five or more peer-reviewed, fully usr_41 compliant plugins
    • Thoroughly document all supported plugins
    • Supervise Workers
    • Assist in the development of reference & resource materials
    • Participate in discussions about best practice for VimL development
  5. Expert
    • Create new tools and libraries for VimL development
    • Create new/interesting/engaging/fun reference material or tutorials for an aspect of Vim/VimL
    • Mentor, guide and train other VimLers
    • Maintain a regular presence on Stack Overflow, the vim-dev mailing lists, #vim or #viml as an authority and guide on advanced Vim and VimL topics

A Plan for Assessing VimL Skills

A central registry of available assessments:
A master github repo called https://github.com/dahu/VimLAssessments.git that contains a list of VimLAss_<level_name>_<assessment_number> github repos in the various skill levels that act as assessments.
  1. Trainee:

  1. Novice:
    • VimLAss_Novice_010 — usr_41 compliance: use <Plug> maps

Creating New VimLAss Assessment Repositories

To create a new VimLAss assessment piece, just copy the VimLAss_Skeleton repository which has the following layout:
  • README.md — an overview of the assessment and a detailed set of tasks to be completed
  • test/<task>.vim — one or more test files per task as listed in the README.md
  • plugin directories with files as necessary. e.g.:
    • autoload/
    • doc/
    • colors/
    • compiler/
    • ftdetect/
    • ftplugin/
    • indent/
    • plugin/
    • syntax/
All VimLAss repositories are to use the https://github.com/vim-scripts/runVimTests.git unit testing framework. The repositories should contain tests for expected behaviour that initially fail. Corresponding tasks in the READEME.md file detail the necessary fixes and enhancements that the vimmler is supposed to implement to get the tests to pass. Successful completion of the assessment begins with having all tests pass. The vimmler should then apply to a Professional/Expert vimmler to have his work reviewed, gain feedback and get his assessment signed off. Actual signoff could involve digital signatures, if that path was ever deemed necessary, which is unlikely.

Even though I have provided some links to various pieces mentioned above, all of this is still very much in thought space at the moment.

I am sure we haven’t covered all bases yet. Do you have anything to contribute?

Saturday, February 9, 2013

SinTax Overdue

Syntax highlighting in Vim sucks.

I know. I haven't done as much of it as you have, but I've heard your cries from my cubicle, your desperate pleas for compassion whispered over and again at your desk to an uncaring Vim, your brave face masking knots of terror while chatting at the water cooler, and your wails of despair in the toilet stall when you thought everyone else had gone. It's been hard watching you go through this and for long now I've wished there was something I could do to ease your burden, to still your trembling hand, wipe the tears from your keyboard and tell you that "It's going to be okay." Of course, I couldn't do that. Nobody could. I'd be lying and you know it. My words would come across as naive, empty platitudes at best or, at worst, taken for cruel taunts to mock your effort, halt your progress and rob you of your due standing among the Nerds of Vim.

That was how we all lived. That is... before THEY came!

SinTax is a Vim plugin that provides a DSL for crafting syntax highlighting files.

It takes this:

" Vim syntax plugin for filetype name.
" Maintainer: Barry Arthur <barry.arthur@gmail.com>
" Israel Chauca F. <israelchauca@gmail.com>
" Version: 0.1
" Description: Long description.
" Last Change: 2013-02-01
" License: Vim License (see :help license)
" Location: syntax/vrs.vim
" Website: https://github.com/Raimondi/vrs

name    vrs
case    ignore
spell   default

keyword vrsTodo    .Todo : TODO FIXME XXX

partial token \S\+\s\+

partial separator
      \\}          # an_escaped_\}
    \|             # or
      [^}]         # anything_but_a_}

match vrsNameErr   .Error      contained : ^\%{token}

match vrsName      .Identifier contained : ^\w\+\s\+

match vrsFlavorErr .Error      contained
    ^\%{token}     # if_the_line_starts_with_a_token
  \)\@<=           #   before
  \%{token}        # a_token

match vrsFlavor    .Type       contained
    ^\%{token}     # if_the_line_starts_with_a_token
  \)\@<=           #   before
  \%{vrsName}      # a_vrsName

match vrsCompItem  .Normal     contained
    \w\+           # a_word
  \|               # or
    \d\+           # a_number
  \|               # or
    ,\@<=          # a_separator_if_proceeded_by_a_comma

" match a composition atom: \%{pattern-name,count,separator}
match vrsCompose   .PreProc    contained contains=vrsCompItem
  \\%{             # a_literal_\{
    \S\+           # a_word_(pattern-name)
    ,              # a_comma
    \d\+           # a_number_(count)
    ,              # a_comma
    \%{separator}* # an_optional_separator
  }                # and_a_literal_}

match vrsRegExp    .String     contains=vrsCompose contained
    ^\%{token,2}   # if_the_line_starts_with_two_tokens
  \)\@<=           #   before
  .*               # anything

match vrsCommand              contains=vrsName,vrsFlavor,vrsNameErr,vrsFlavorErr,vrsRegExp,vrsComment
  ^\%{token,2}\S.* # a_line_with_three_'tokens'_minimum

match vrsContinued .String     contains=vrsComment
  ^\s\+\S.*        # a_line_with_leading_whitespace_and_a_'token'

match vrsComment   .Comment    containedin=ALL contains=vrsTodo
  \%(              # as_long_as
      \\ \\        #   (ignoring_any_number_of_double_backslashes_(\\))
    \\             #   a_backslash
  \)\@<!           # doesn't_precede
  #.*$             # a_literal_#_followed_by_anything

match vrsError     .Error
  ^                # any_line_starting_with
  [^a-zA-Z0-9_#\ ] # anything_that's_not_alphanumeric,_underscore,_hash_or_a_space
  .*               # and_anything_afterwards

And generates this:

" Vim syntax plugin for filetype name.
" Maintainer: Barry Arthur <barry.arthur@gmail.com>
" Israel Chauca F. <israelchauca@gmail.com>
" Version: 0.1
" Description: Long description.
" Last Change: 2013-02-01
" License: Vim License (see :help license)
" Location: syntax/vrs.vim
" Website: https://github.com/Raimondi/vrs

" Quit when a (custom) syntax file was already loaded
if exists("b:current_syntax")

" Allow use of line continuation.
let s:save_cpo = &cpo
set cpo&vim

syntax case ignore
syntax spell default
syntax keyword vrsTodo  TODO FIXME XXX 
syntax match vrsNameErr /^\S\+\s\+/ contained 
syntax match vrsName /^\w\+\s\+/ contained 
syntax match vrsFlavorErr /\%(^\S\+\s\+\)\@<=\S\+\s\+/ contained
syntax match vrsFlavor /\%(^\S\+\s\+\)\@<=^\w\+\s\+/ contained
" match a composition atom: \%{pattern-name,count,separator}
syntax match vrsCompItem /\w\+\|\d\+\|,\@<=\%(\\}\|[^}]\)\+/ contained
syntax match vrsCompose /\\%{\S\+,\d\+,\%(\\}\|[^}]\)*}/ contained contains=vrsCompItem
syntax match vrsRegExp /\%(^\S\+\s\+\S\+\s\+\)\@<=.*/ contains=vrsCompose contained
syntax match vrsCommand /^\S\+\s\+\S\+\s\+\S.*/ contains=vrsName,vrsFlavor,vrsNameErr,vrsFlavorErr,vrsRegExp,vrsComment
syntax match vrsContinued /^\s\+\S.*/ contains=vrsComment
syntax match vrsComment /\%(\%(\\\\\)*\\\)\@<!#.*$/ containedin=ALL contains=vrsTodo
syntax match vrsError /^[^a-zA-Z0-9_#\ ].*/ 
syntax match vrsError /foo/ 

hi def link vrsTodo Todo
hi def link vrsNameErr Error
hi def link vrsName Identifier
hi def link vrsFlavorErr Error
hi def link vrsFlavor Type
hi def link vrsCompItem Normal
hi def link vrsCompose PreProc
hi def link vrsRegExp String
hi def link vrsContinued String
hi def link vrsComment Comment
hi def link vrsError Error
hi def link vrsError Error

let b:current_syntax = "vrs"

let &cpo = s:save_cpo
unlet s:save_cpo

" vim: set sw=2 sts=2 et fdm=marker:

Now I feel more equipped to take your hand and say, "there, there."

Depends On: Raimondi's VimRegStyle
Coming Soon! SinTax is still in development but is ready for user testing. Feedback welcome.

Saturday, February 2, 2013

Evimosaurus Rex


because everyone deserves extended regular expressions

A couple posts back I compared some idiomatic Ruby with equivalent Vim forms. One of those was the multiline, whitespace-insensitive extended regular expression mode that the /x flag gives the PCRE wielder. I showed how this might be achieved in Vim as:

let PHONE_NUMBER_PATTERN = substitute(substitute('
      \ ^
      \ \%(
      \   \(\d\)           # prefix_digit
      \   [\ \-\.]\?       # optional_separator
      \ \)\?
      \ \%(
      \   (\?\(\d\{3}\))\? # area_code
      \ [\ \-\.]           # separator
      \ \)\?
      \ \(\d\{3}\)         # trunk
      \ [\ \-\.]           # separator
      \ \(\d\{4}\)         # line
      \ \%(:\ \?x\?        # optional_space_or_x
      \   \(\d\+\)         # extension
      \ \)\?
      \ $', '# \S\+', '', 'g'), '\\\@<! ', '', 'g')

let a_phone_number = '1-234-567-0987:1234'

echo matchlist(a_phone_number, PHONE_NUMBER_PATTERN)

Which is all good and well, but wouldn’t it be nicer if we could just do this instead:

      \ ^
      \ \%(
      \   \(\d\)           # prefix_digit
      \   [\ \-\.]\?       # optional_separator
      \ \)\?
      \ \%(
      \   (\?\(\d\{3}\))\? # area_code
      \ [\ \-\.]           # separator
      \ \)\?
      \ \(\d\{3}\)         # trunk
      \ [\ \-\.]           # separator
      \ \(\d\{4}\)         # line
      \ \%(:\ \?x\?        # optional_space_or_x
      \   \(\d\+\)         # extension
      \ \)\?
      \ $')

let a_phone_number = '1-234-567-0987:1234'

echo matchlist(a_phone_number, PHONE_NUMBER_PATTERN)

Where the ERex object was just magically waiting in the background for all of our extended regex needs…?

Install https://github.com/Raimondi/VimRegStyle and you can!

“There is no charge for awesomeness.”
— Po

This just in! the awesomeness of Extended Regular Expressions has just been added to vimple.

RFC on VimRegStyle


more than just a pattern library for sexy regex

This is a request for feedback on a new plugin: https://github.com/Raimondi/VimRegStyle

VimRegStyle is designed to be a repository of PCRE ←→ Vim regex equivalences and general pattern library for Vimmers.

Our goal is to have somewhere for the collection of common regex patterns expressed in the Vim regex flavour. We frequently get regex help requests on #vim that are answered with “look that common pattern up on a regex lib site” only to have them come back and say “it didn’t work” because they plugged the PCRE into Vim and got spanked for it.

No more! Now we have a library of our own!

So… what do I want from you? Feedback on:
  1. Design issues (concerns & improvements)(*)
  2. Ideas for tools, commands, maps and scripts surrounding such a pattern library.
(*) This might be the place to mention that we’ve taken several rather bold steps in the implementation of the pattern repository files:
  1. the patterns/ directory contains *.vrs files with the following format:
    name flavour pattern
    • name contains no whitespace
    • flavour can be vim or pcre
    • pattern is not delimited — use a bare regex
  2. the patterns are further enhanced in the following two ways; they:
    • accept PCRE style multiline, whitespace insensitive syntax. All multiline patterns must commence on the line below the named entry and must be indented with whitespace.
    • accept a new regex atom: \%{name,count,separator} providing pattern composition by inline-expanding the named pattern at the current point in the regex (optionally count times, each one separated by separator.)

      As an example:, assuming the VRS library had a pattern called _ip4_segment that represented a single 0-255 chunk, an ip4 regex could then be written using this composition atom as: \<\%{_ip4_segment,4,.}>
      As a side note, the Extended Regex features mentioned here will be further elaborated on in a separate article. These features can be freely used in other projects, pulling from arbitrary lookup sources, including the runtime vars in Vim itself. But more on that later.
When we’re finished with this RFC process we will be looking for pattern contributions. Thanks to all who contribute their time and energy into this project! :-)

Monday, January 28, 2013

Say it with VimL

I like Ruby. She’s a beautiful language. So expressive and elegant and yummy. VimL is Vim’s scripting language. While she may not win the sort of aesthetic awards Ruby deserves, she certainly is expressive and elegant in her own way.
Gregory Brown recently showed a handful of idioms for elegantly working with text and files in Ruby. I thought I’d show their VimL analogues here.

idioms for text processing

1. Multiline Matches

Vim has its own regular expression flavour. It’s a bit shocking to PCRE lovers at first — it uses an older, more arcane syntax that can reduce the most ardent Perler to pitiful puling instead. Sulk as they may though, Vim’s regex flavour got here before PCRE and isn’t going anywhere fast. The good news is that Vim’s regex flavour is quite strong — equally up to the machinations of PCRE in almost all aspects (and certainly so in all that count within the context of editing text). I digress — this is not the place to wage that war.
Gregory showed the PCRE idiom of using the /s flag<*> to enable DOTALL mode which allows the . atom to match newlines (as well as its default match-any-character behaviour.) Vim uses \_. to achieve this result:

echo matchlist("foo\nbar\nbaz\nquux", 'foo\n\(\_.*\)quux')[1]

<*> The astute reader will have noticed my sleight play there. Ruby’s flavour of PCRE uses the /m flag to mean what the rest of the PCRE speaking world knows /s to do. I must admit, I was scratching my head when I first read Gregory’s article thinking he’d given the wrong example to suit the /m flag. Thanks goes to kotigid on #regex for pointing me at the Ruby regex page.

2. matchlist()

While Vim doesn’t have the global match variables ($1 et al) that Gregory is recommending avoidance of, it does have his preferred method baked right in. The matchlist() function returns a list containing the whole match as the zeroth element and any submatches from index 1 onwards.

echo matchlist("---\na\nb\nc\n---\n", '^\(---\s*\n\_.\{-}\n\?\)\(---\s*\n\?\)')

3. Extended Regular Expression Syntax

The /x flag in PCRE allows complex regular expressions to be spread out over multiple lines with embedded comments for easier readability and clarity. We can approximate that in VimL:

let PHONE_NUMBER_PATTERN = substitute(substitute('
      \ ^
      \ \%(
      \   \(\d\)           # prefix_digit
      \   [\ \-\.]\?       # optional_separator
      \ \)\?
      \ \%(
      \   (\?\(\d\{3}\))\? # area_code
      \ [\ \-\.]           # separator
      \ \)\?
      \ \(\d\{3}\)         # trunk
      \ [\ \-\.]           # separator
      \ \(\d\{4}\)         # line
      \ \%(:\ \?x\?        # optional_space_or_x
      \   \(\d\+\)         # extension
      \ \)\?
      \ $', '# \S\+', '', 'g'), '\\\@<! ', '', 'g')

let a_phone_number = '1-234-567-0987:1234'

echo matchlist(a_phone_number, PHONE_NUMBER_PATTERN)

4. Using join()

VimL doesn’t have string interpolation like Ruby.
Given a dictionary (a.k.a associative array, or hash) such as:

let filedata = {'year' : 2013, 'month' : 1, 'day' : 28}

To include variable values in strings we have to use catenation:

echo filedata["year"] . '/' . filedata["month"]. '/' .  filedata["day"]

Of course, the join() trick Gregory showed also works in VimL:

echo join([filedata["year"], filedata["month"], filedata["day"] ], "/")

Another approach in both languages would be to use a printf string:

echo printf("%d/%d/%d",filedata["year"], filedata["month"], filedata["day"])

On the down side, this only works when you know how many fields you need to print, and you’re forced to insert the / characters manually. On the up side, you can easily format the values to show, for example, leading zeros in the day and month fields:

echo printf("%d/%02d/%02d",filedata["year"], filedata["month"], filedata["day"])

idioms for working with files and folders

1. Filenames

Ruby has File.dirname, File.basename, and File.extname for munging filenames. Vim uses the expand() function to do this. Ruby’s FILE (available in Vim as % and VimL as expand('%')) is expressed in Vim as:

echo expand('%:p')

The :p there is called a Modifier in the :help expand() docs. The :p modifier means full path.

To get the dirname only (called the head in vimspeak):

echo expand('%:p:h')

To get the basename (called tail):

echo expand('%:p:t')

Which will return the basename.extension form of the filename. To get just the basename with no extension, use the :r (root) modifier to strip off one level of extension:

echo expand('%:p:t:r')

To get the extension (mnemonically equivalent in vimspeak):

echo expand('%:p:e')

2. Pathname Objects

The closest analogue in Vim to Pathname objects is the fnamemodify() function which provides the same filename manipulations as the expand() function above. You can find more functions like this in :help file-functions.

3. Reading and Writing Files

Vim has two builtin functions for reading and writing files: readfile(fname) (which returns a list of lines) and writefile(list, fname). Semantically simple interfaces.

4. Dir.mktmpdir

Vim doesn’t have a mktmpdir() function but more importantly, VimL doesn’t have the beautiful code blocks of Ruby. As such, we have to use a more procedural idiom of manually creating a temporary directory (with :help tempname()), doing what we want in it and finally remembering to clean up after ourselves. Ruby wins here.


Gregory’s intent behind his article was to lead the misguided Rubiest away from using needlessly laborious low-level functions for achieving what can be more beautifully expressed using idiomatic Ruby and elegant thinking. My intent with this article is twofold: firstly to show that not only can VimL easily do the sort of text and file manipulations Gregory showed, but also in most cases just as elegantly (read: semantically simple). Sure, VimL’s actual syntax in places might make your skin crawl, but once you overcome that and appreciate the deeper aesthetics, VimL doesn’t deserve the derision it receives as being a gnarled and impotent language.