short and sweet LISP editing

Table of Contents

• Introduction
  • Relation to vi
  • Features
  • Function reference
• Getting Started
  • Installation instructions
    • via MELPA
    • via el-get
  • Configuration instructions
  • Customization instructions
• Operating on lists
  • How to get into list-editing mode (special)
  • Digit keys in special
  • How to get out of special
  • List commands overview
    • Inserting pairs
    • Reversible commands
    • Keys that modify whitespace
    • Command chaining
    • Navigating with avy-related commands
• Operating on regions
  • Ways to activate region
  • Move region around
  • Switch to the other side of the region
  • Grow/shrink region
  • Commands that operate on region
• IDE-like features
• Demos
  • [Demo 1: Practice generating code](#demo-1-practice-generating-codehttpabo-abogithubiolispydemo-1)
  • [Demo 2: The substitution model for procedure application](#demo-2-the-substitution-model-for-procedure-applicationhttpabo-abogithubiolispydemo-2)
  • [Demo 3: Down the rabbit hole](#demo-3-down-the-rabbit-holehttpabo-abogithubiolispydemo-3)
  • [Demo 4: Project Euler p100 and Clojure](#demo-4-project-euler-p100-and-clojurehttpabo-abogithubiolispydemo-4)
  • [Demo 5: ->>ification](#demo-5--ificationhttpabo-abogithubiolispydemo-5)
  • [Demo 6: cond->if->cond](#demo-6-cond-if-condhttpabo-abogithubiolispydemo-6)
• Screencasts

Introduction

This package reimagines Paredit - a popular method to navigate and edit LISP code in Emacs.

The killer-feature are the short bindings:

Most of more than 100 interactive commands that lispy provides are bound to a-z and A-Z in lispy-mode. You can see the full command reference with many examples here.

The price for these short bindings is that they are only active when:

• the point is before an open paren: (, [ or {
• the point is after a close paren: ), ] or }
• the region is active

The advantage of short bindings is that you are more likely to use them. As you use them more, you learn how to combine them, increasing your editing efficiency.

To further facilitate building complex commands from smaller commands, lispy-mode binds digit-argument to 0-9. For example, you can mark the third element of the list with 3m. You can then mark third through fifth element (three total) with 2> or >>. You can then move the selection to the last three elements of the list with 99j.

If you are currently using Paredit, note that lispy-mode and paredit-mode can actually coexist with very few conflicts, although there would be some redundancy.

Relation to vi

The key binding method is influenced by vi, although this isn't modal editing per se.

Here's a quote from Wikipedia on how vi works, in case you don't know:

vi is a modal editor: it operates in either insert mode (where typed text becomes part of the document) or normal mode (where keystrokes are interpreted as commands that control the edit session). For example, typing i while in normal mode switches the editor to insert mode, but typing i again at this point places an "i" character in the document. From insert mode, pressing ESC switches the editor back to normal mode.

Here's an illustration of Emacs, vi and lispy bindings for inserting a char and calling a command:

Advantages/disadvantages:

• Emacs can both insert and call commands without switching modes (since it has none), but the command bindings are long
• vi has short command bindings, but you have to switch modes between inserting and calling commands
• lispy has short command bindings and doesn't need to switch modes

Of course it's not magic, lispy needs to have normal/insert mode to perform both functions with j. The difference from vi is that the mode is explicit instead of implicit - it's determined by the point position or the region state:

• you are in normal mode when the point is before/after paren or the region is active
• otherwise you are in insert mode

So people who generally like Emacs bindings (like me) can have the cake and eat it too (no dedicated insert mode + shorter key bindings). While people who like vi can still get an experience that's reasonably close to vi for LISP editing (since vi's line-based approach isn't very appropriate for LISP anyway).

But if you ask:

What if I want to insert when the point is before/after paren or the region is active?

The answer is that because of the LISP syntax you don't want to write this:

j(progn
   (forward-char 1))k

Also, Emacs does nothing special by default when the region is active and you press a normal key, so new commands can be called in that situation.

Features

• Basic navigation by-list and by-region:

  • h moves left
  • j moves down
  • k moves up
  • l moves right
  • f steps inside the list
  • b moves back in history for all above commands

• Paredit transformations, callable by plain letters:

  • > slurps
  • < barfs
  • r raises
  • C convolutes
  • s moves down
  • w moves up

• IDE-like features for Elisp, Clojure, Scheme, Common Lisp, Hy, Python and Julia:

  • e evals
  • E evals and inserts
  • g jumps to any tag in the current directory with semantic
  • G jumps to any tag in the current file
  • M-. jumps to symbol, M-, jumps back
  • F jumps to symbol, D jumps back
  • C-1 shows documentation in an overlay
  • C-2 shows arguments in an overlay
  • Z breaks out of edebug, while storing current function's arguments

Some pictures here.

• Code manipulation:
  • i prettifies code (remove extra space, hanging parens ...)
  • xi transforms cond expression to equivalent if expressions
  • xc transforms if expressions to an equivalent cond expression
  • x> transforms expressions from/to an equivalent thread-last expression
  • xf flattens function or macro call (extract body and substitute arguments)
  • xr evals and replaces
  • xl turns current defun into a lambda
  • xd turns current lambda into a defun
  • O formats the code into one line
  • M formats the code into multiple lines
• Misc. bindings:
  • outlines navigation/folding (J, K, I, i)
  • narrow/widen (N, W)
  • ediff (b, B)
  • ert (T)
  • edebug (xe)

Function reference

Most functions are cataloged and described at http://abo-abo.github.io/lispy/.

Getting Started

Installation instructions

via MELPA

It's easiest/recommended to install from MELPA. Here's a minimal MELPA configuration for your ~/.emacs:

(package-initialize)
(add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/"))

Afterwards, M-x package-install RET lispy RET (you might want to M-x package-refresh-contents RET beforehand if you haven't done so recently).

via el-get

el-get also features a lispy recipe. Use M-x el-get-install RET lispy RET to install.

Configuration instructions

Enable lispy automatically for certain modes

After installing, you can call M-x lispy-mode for any buffer with a LISP dialect source. To have lispy-mode activated automatically, use something like this:

(add-hook 'emacs-lisp-mode-hook (lambda () (lispy-mode 1)))

Enable lispy for eval-expression

Although I prefer to eval things in *scratch*, sometimes M-: - eval-expression is handy. Here's how to use lispy in the minibuffer during eval-expression:

(defun conditionally-enable-lispy ()
  (when (eq this-command 'eval-expression)
    (lispy-mode 1)))
(add-hook 'minibuffer-setup-hook 'conditionally-enable-lispy)

Customization instructions

If you want to replace some of the lispy-mode's bindings you can do it like this:

(eval-after-load "lispy"
  `(progn
     ;; replace a global binding with own function
     (define-key lispy-mode-map (kbd "C-e") 'my-custom-eol)
     ;; replace a global binding with major-mode's default
     (define-key lispy-mode-map (kbd "C-j") nil)
     ;; replace a local binding
     (lispy-define-key lispy-mode-map "s" 'lispy-down)))

Compatibility with other modes

Use the lispy-compat variable to enable compatibility with modes that could otherwise conflict. These currently include:

• god-mode
• magit-blame-mode
• edebug
• cider
• macrostep

The default setting only enables compatibility with edebug.

Operating on lists

How to get into list-editing mode (special)

The plain keys will call commands when:

• the point is positioned before paren
• the point is positioned after paren
• the region is active

When one of the first two conditions is true, I say that the point is special. When the point is special, it's very clear to which sexp the list-manipulating command will be applied to, what the result be and where the point should end up afterwards. You can enhance this effect with show-paren-mode or similar.

Here's an illustration to this effect, with lispy-clone (here, | represents the point):

You can use plain Emacs navigation commands to get into special, or you can use some of the dedicated commands:

These are the few lispy commands that don't care whether the point is special or not. Other such bindings are DEL, C-d, C-k.

Special is useful for manipulating/navigating lists. If you want to manipulate symbols, use region selection instead.

Digit keys in special

When special, the digit keys call digit-argument which is very useful since most lispy commands accept a numeric argument. For instance, 3c is equivalent to ccc (clone sexp 3 times), and 4j is equivalent to jjjj (move point 4 sexps down).

Some useful applications are 9l and 9h - they exit list forwards and backwards respectively at most 9 times which makes them effectively equivalent to end-of-defun and beginning-of-defun. Or you can move to the last sexp of the file with 999j.

How to get out of special

To get out of the special position, you can use any of the good-old navigational commands such as C-f or C-n. Additionally SPC will break out of special to get around the situation when you have the point between the open parens like this

(|(

and want to start inserting; SPC will change the code to this:

(| (

List commands overview

Inserting pairs

Here's a list of commands for inserting pairs:

Reversible commands

A lot of Lispy commands come in pairs - one reverses the other:

Keys that modify whitespace

These commands handle whitespace in addition to inserting the expected thing.

Command chaining

Most special commands will leave the point special after they're done. This allows to chain them as well as apply them continuously by holding the key. Some useful hold-able keys are jkf<>cws;. Not so useful, but fun is /: start it from |( position and hold until all your Lisp code is turned into Python :).

Navigating with avy-related commands

q - lispy-ace-paren jumps to a "(" character within current top-level form (e.g. defun). It's much faster than typing in the avy binding + selecting "(", and there's less candidates, since they're limited to the current top-level form.

a - lispy-ace-symbol will let you select which symbol to mark within current form. This can be followed up with e.g. eval, describe, follow, raise etc. Or you can simply m to deactivate the mark and edit from there.

- - lispy-ace-subword is a niche command for a neat combo. Start with:

(buffer-substring-no-properties
 (region-beginning)|)

Type c, -, b and C-d to get:

(buffer-substring-no-properties
 (region-beginning)
 (region-|))

Fill end to finish the statement.

Operating on regions

Sometimes the expression that you want to operate on isn't bounded by parens. In that case you can mark it with a region and operate on that.

Ways to activate region

While in special:

• Mark a sexp with m - lispy-mark-list
• Mark a symbol within sexp a - lispy-ace-symbol.

While not in special:

• C-SPC - set-mark-command
• mark a symbol at point with M-m - lispy-mark-symbol
• mark containing expression (list or string or comment) with C-M-, - lispy-mark

Move region around

The arrow keys j/k will move the region up/down within the current list. The actual code will not be changed.

Switch to the other side of the region

Use d - lispy-different to switch between different sides of the region. The side is important since the grow/shrink operations apply to current side of the region.

Grow/shrink region

Use a combination of:

• > - lispy-slurp - extend by one sexp from the current side. Use digit argument to extend by several sexps.
• < - lispy-barf - shrink by one sexp from the current side. Use digit argument to shrink by several sexps.

The other two arrow keys will mark the parent list of the current region:

• h - lispy-left - mark the parent list with the point on the left
• l - lispy-right - mark the parent list with the point on the right

To do the reverse of the previous operation, i.e. to mark the first child of marked list, use i - lispy-tab.

Commands that operate on region

• m - lispy-mark-list - deactivate region
• c - lispy-clone - clone region and keep it active
• s - lispy-move-down - move region one sexp down
• w - lispy-move-up - move region one sexp up
• u - lispy-undo - deactivate region and undo
• t - lispy-teleport - move region inside the sexp you select with lispy-ace-paren
• C - lispy-convolute - exchange the order of application of two sexps that contain region
• n - lispy-new-copy - copy region as kill without deactivating the mark
• P - lispy-paste - replace region with current kill

IDE-like features

These features are specific to the Lisp dialect used. Currently Elisp and Clojure (via cider) are supported. There's also basic evaluation support for:

• Scheme (via geiser)
• Common lisp (via slime or sly).
• Hy (via comint).
• Python (via comint and jedi).
• Julia (via julia-shell).

lispy-describe-inline

Bound to C-1. Show the doc for the current function inline.

C-h f is fine, but the extra buffer, and having to navigate to a symbol is tiresome. C-1 toggles on/off the inline doc for current function. No extra buffer necessary:

Here's how it looks for Clojure:

lispy-arglist-inline

Bound to C-2. Show arguments for current function inline.

eldoc-mode is cool, but it shows you arguments over there and you're writing over here!. No problem, C-2 fixes that:

As you see, normal, &optional and &rest arguments have each a different face. Here's how it looks for Clojure:

lispy-goto

Bound to g.

Use completion to select a symbol to jump to from all top-level symbols in the in current directory.

Works out of the box for Elisp, Scheme and Common Lisp. clojure-semantic is required for Clojure.

lispy-eval

There's a feature similar to ipython-notebook. Evaluating an Emacs outline will evaluate all of the outline's code and echo the result of the last expression. When an outline ends with a colon (:), the result will instead be inserted into the buffer. If the evaluation result changes for whatever reason, it will be replaced after each subsequent e.

Python, Clojure, and Julia currently have a slightly better notebook support, pressing e on the parent outline will evaluate all the children outlines sequentially. This allows to arrange scripts hierarchically, with relatively few top-level outlines and relatively many total outlines. Each outline's output can be examined by adding a : to the title of the outline.

The following example shows a buffer before and after pressing e.

There is one top-level outline, with one level-2 child, which in turn has a four level-3 children. Three of these children end in :, so their output will be updated after the eval.

Demos

Demo 1: Practice generating code

Demo 2: The substitution model for procedure application

Demo 3: Down the rabbit hole

Demo 4: Project Euler p100 and Clojure

Demo 5: ->>ification

Demo 6: cond->if->cond

Screencasts

• The older stuff can be found on vimeo.
• The newer stuff is on https://www.youtube.com/user/abo5abo/videos.