Extending the Vim Language

The Weekly Iteration

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Video

Notes

Refresher on Vim Command Language

We recommend going through our Onramp to Vim course on Vim's command language before this video, so that you're comfortable with the topics discussed in this video.

Now let's build on the ideas from Onramp to Vim to use them to even better effect.

Vim's command language

The Vim language is the unique structure of key mappings in Vim such that we can almost treat it like a language. For example, vip breaks down into:

  • v: visually select
  • i: inner
  • p: paragraph (Vim calls this a "text object")

So vip is "visually select inner paragraph". Since we know ip, we can use it with other verbs like d ("delete"), and we know what e.g. dip will do: delete inner paragraph. We can expand this to other verbs and nouns, like ciw:

  • c: change
  • i: inner
  • w: word

We can use . to repeat this action as well, and Vim will "change a word" on any word the cursor is on. It works with any word, not just the original word we typed ciw on. We can compose our changes almost like a sentence.

Custom verbs and nouns

Sometimes we find that we don't have the right verb or noun for a change that we want to make. Luckily, Vim has a plugin system!

vim-commentary

The Commentary Vim plugin gives us a new verb that comments things out. Chris has it mapped to cm, so we can do things like cmip to comment out a paragraph. Commentary is also filetype-aware, so it will use the correct comment character for the current file you're editing.

exchange.vim

Exchange is for exchanging words, or any other text object. Its mapping is cx, so cxiw will exchange a word, cxip will exchange a paragraph, and so on. Exchange gives us a new verb that works with all of our adjectives (like "inner") and nouns (like "word" or "paragraph").

ReplaceWithRegister

ReplaceWithRegister gives us the ability to replace the text under the cursor with yanked text. If we yank "before_save", then put our cursor on another word and type griw ("go replace inner word"), this plugin will replace the word under the cursor with "before_save". Just like all of our other operators, we can repeat this using ..

Even better, we can use this with any register, and there's a special register that points to the system clipboard. Using this knowledge and ReplaceWithRegister, we can paste over words (or sentences, or paragraphs) with the contents of the system clipboard using this mapping:

" Note, this must be nmap, not nnoremap
nmap <leader>gr "*gr

(You can install this plugin with the vim-scripts GitHub mirror.)

Surround

We covered Surround in our video on Vim plugins, but we use it so much that we're talking about it again. surround.vim gives us some very handy operators for changing what surrounds a text object. For example, given name, we can change it to "name" by putting our cursor on the word and typing ysiw", which means "surround inner word with double quotes".

We can change the surrounding punctuation by putting our cursor on "name" and typing csiw', which means "change surroundings of inner word to double quotes".

Sort motion

sort-motion gives you a verb that you can use to sort a range of lines easily with any line-based text object or motion. Its verb is gs ("go sort"), so gs2j will sort the next two lines.

TitleCase

titlecase title-cases a sentence. It's quite handy in prose documents (like Markdown). Its mapping is gt ("go titlecase"), so gti" will titlecase words inside double quotes.

SystemCopy

system-copy gives you mappings for copying to and pasting from the system clipboard. Some people connect their Vim clipboard to the system clipboard directly, but that means copying any text outside of Vim overwrites any text you've yanked in Vim, and vice versa. Instead of each one overwriting the other, system-copy makes the system clipboard readily available to Vim while keeping them separate.

Custom Text Objects

text-obj-user

text-obj-user is foundational; end-users don't use it directly, but many other plugins require it and you'll need to have it installed to use the plugins below.

Entire

entire allows us to operate on the entire document. Its text object is called ae, so we could do yae to yank the entire document, or cpae (combined with system-copy, above) to copy the entire document.

Indent

indent text object lets us operate on text that's at the same indentation level. We can do gsii to go sort (gs) inner (i) indent (i).

Line

line lets us operate on a line, ignoring leading whitespace. yil will yank inner line (only the part that has the dashed line over it):

    ---------
    gem "hey"

We can also use gril to replace the current line with the text we've yanked.

Vim is about the Language

For more text objects you can check out the text-object wiki. The key is to embrace the idea that Vim has a language of verbs and nouns. You should learn the built-in ones first, but you'll hit a wall where Vim doesn't understand, or can't do, things that you want it to do. Fortunately with these plugins, we can tell Vim about totally new ways to select and operate on text.

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