express.vim

Express yourself with custom operators. Define your own operators that apply either a VimL expression or a substitution to any motion or text object.

Custom operators

Express

Expression opertors are created using the :MapExpress command. The expression makes use of the v:val placeholder, which contains the text covered by the given motion, and returns a string.

For example, to create an operator cd that surrounds a motion in C-style comment delimiters, you can use the following command:

:MapExpress cd '/* ' . v:val . ' */'

Now you can use the new operator cd on any motion or text object, such as cdiw to comment out a word, or cdi( to comment out everything inside parentheses.

Subpress

Substitution operators are created using the :MapSubpress command. The substitution takes a form much like that of the :substitute command. It contains a search pattern, a replacement, and flags, each surrounded by some delimiter.

As an example, to create an operator yc that capitalizes each word of a motion, you can use the following command:

:MapSubpress yc /\<\w/\u\0/g

Now you can use the yc operator on any motion or text object, such as yc) to capitalize from the cursor to the beginning of the next sentence, or ycap to capitalize every word in the paragraph.

NOTE

At the time of loading your .vimrc file, the commands :MapExpress and :MapSubpress will likely not have been defined yet. To create operators using these commands in your .vimrc, you can use the VimEnter event, for example:

autocmd VimEnter * MapExpress cd '/*' . v:val . ' */'

Ad-hoc operators

Sometimes you just want to do a one-off (but repeatable) operation using a VimL expression or substitution. The g= and g: operators will let you do just that.

g={motion}

Replace the text defined by {motion} with the value of an expression. The expression is entered at the command-line after a = prompt. The original text will populate the value of v:val within the expression.

g:{motion}

Filter the text defined by {motion} through a :substitute-like command. This is basically the same as using g= and entering substitute(v:val, ...), but it's a bit easier (and more familiar) to type. A substitution is entered at the command-line after a :s/ prompt. The / character in the prompt can be deleted and replaced with a different delimiter.

Examples

Here are some examples of using the g= and g: operators. In the examples, the prompt is included in the Expression column. For g= operations, the prompt is =; for g: operations, the prompt is :s/. The complete operation is performed by typing the Operator + Motion followed by the Expression (without the prompt), and then pressing Enter.

Note that both operators are repeatable with . when repeat.vim is installed.

Description	Operator + Motion	Expression	Before	After
Change member names to getters (snake case)	g=iw	='get_'.v:val.'()'	foo_bar	get_foo_bar()
Change member names to getters (camel case)	g:iw	:s/.*/get\u\0()/	fooBar	getFooBar()
Sort elements of an array literal	g=i[	=join(sort(split(v:val, ', ')), ', ')	[foo, bar, baz]	[bar, baz, foo]
Clean up whitespace around binary operators	g:: (line)	:s/\s*\([=+*\/-]\)\s*/ \1 /g	int x=foo + bar *baz	int x = foo + bar * baz
Comment out a block of code	g=ip	='/* '.v:val.' */'	int x = 400; int y = 5;	/* int x = 400; int y = 5; */

Operators taking user input

Some operators take input from the user to perform a change. Without some etra setup, repeating the operaton with . would prompt the user for input again. To help avoid this, express.vim offers an interface to use in operator definitions that hook into repeat.vim.

Capturing user input

To make user input automatically inserted upon repeat (using .), enclose the part of code that prompts for input in express#capture().

For example, if defining an operator to replace all characters with a character input by the user, you can capture the use input as follows:

:MapSubpress cr /./\=express#capture(nr2char(getchar()))/g

Some methods of user input require additional keystokes such as pressing Enter to terminate the input sequence. To accomodate for this, additional characters can be provided as a second argument to express#capture(). For example, appending a user-input string to the end of the motion:

:MapExpress dc v:val . express#capture(input('Suffix: '), "\<CR>")

Here, "\<CR>" is the carriage return typed after inputting a string with input(). The result of the function does not include the carriage return, but the user must type it to terminate input.

Recalling captured input

If you want a value taken from a single input prompt to be used in multiple places in your operator's expression, you can recall any portion captured by express#capture() using express#recall(n), where n is the position of the call to express#capture() in the expression (similar to backreferences in regex).

For example, to enclose a motion in an input string, we can do something like this:

:MapExpress yp express#capture(input('Enclosing: '), "\<CR>") . v:val . express#recall(1)