Paredit Preso

Bay Area Clojure Meetup
functional lispers

December 3, 2009
Runa Galactic Headquarters

Friday, December 4, 2009

paredit
At ﬁrst it sucks, but then it’s awesome.

mudphone (kyle oba)
irc / twitter / github
runa employee 9

about runa
We are simultaneously the largest cloud-based
manufacturer, distributor, and consumer of
Bavarian-style pretzels, nationally.
http://www.ﬂickr.com/photos/bellalago/3938498023/

and we’re hiring
clojure-hbase-ruby-hadoop-rails-javascript-chefs


0/8 why


Q: What is paredit?

A: paredit is a minor mode for Emacs,
created by Taylor R. Campbell.


commit 2ecf00a124062d7b4c4538f79426bc19c6b11b83
Author: Philip (ﬂip) Kromer <ﬂip@infochimps.org>
Date: Mon Aug 24 23:38:14 2009 -0500

Paredit fucking sucks my balls

So, why paredit?


Because, these are your father’s parentheses...

http://xkcd.com/297/


http://technomancy.us/126

Hingebjerg – 2009-06-01T14:05:40Z
Hi Phil,

Just installed the emacs-starter-kit and clojure-mode, and i can't delete
curly braces when in clojure-mode. Is there a logical explanation for that?

Phil – 2009-06-12T09:37:15Z
Hingebjerg: That's a feature of paredit-mode; it enforces that you can't
delete parens (or other matched chars) unless they're empty so you
don't end up with invalid structure in your code. It's unbelievably handy/
addictive once you get used to it, but if you're not sure what's going on it
can be pretty annoying.


0/8 why
1/8 balancing
2/8 basic insertion commands
3/8 deleting & killing
4/8 movement & navigation
5/8 depth-changing commands
6/8 barfage & slurpage
7/8 miscellaneous commands
8/8 in the wild (tips & tricks)


1/8 balancing


balancing basics

keys

([“ ([“”])


1.1/8 assumptions


you’re using the emacs starter kit
or, you’re already familiar setting the modes up

you’ve got paredit and show-parens modes
M-x paredit-mode
M-x show-paren-mode


install?

;;; Install paredit by placing `paredit.el' in `/path/to/elisp', a
;;; directory of your choice, and adding to your .emacs ﬁle:
;;;
;;; (add-to-list 'load-path "/path/to/elisp")
;;; (autoload 'paredit-mode "paredit"
;;; "Minor mode for pseudo-structurally editing Lisp code."
;;; t)
;;;
;;; Toggle Paredit Mode with `M-x paredit-mode RET', or enable it
;;; always in a major mode `M' (e.g., `lisp' or `scheme') with:
;;;
;;; (add-hook M-mode-hook (lambda () (paredit-mode +1)))

http://mumble.net/~campbell/emacs/paredit.el


wrapping
killing
raising
splicing
slurping / barﬁng
1.2/8 demo splitting / joining


2/8 basic insertion commands


paredit-open-round

keys
(a b |c d)
(
(a b (|) c d)


paredit-close-round-and-newline

keys (a b |c )
) (a b c)
|


paredit-close-round

keys
(a b |c )
M-)
(a b c)|


paredit-open-square

keys
(a b |c d)
[
(a b [|] c)


paredit-close-square

keys
(defn cky [bcn| ] 2)
]
(defn cky [bcn]| 2)


paredit-doublequote

keys
(ça va |bien)
“
(ça va “|” bien)


paredit-doublequote
(while in a quote)

keys
(the “q|uick” fox)
“
(the “q”|uick” fox)


paredit-meta-doublequote

keys
(the |(cky) bcn)
M-”
(the “|(cky)” bcn)


paredit-meta-doublequote
(while in quote)

keys (the “chk|y” bcn)
M-” (the “chky”
|bcn)


paredit-comment-dwim

keys
(blah |xyz) ; baz
M-;
(blah xyz) ; |baz



keys
(amit siva)|
M-;
(amit siva) ;|



(hbase)
|
keys (clojure)
M-; (hbase)
;;; |
(clojure)


(ruby) |(java)
keys

M-; (ruby)
;;; |
(java)

paredit-newline

keys (let [x 2] |(list x y)
C-j (let [x 2]
|(list x y))


intermission


3/8 deleting & killing


paredit-forward-delete

(|”third” worst)
keys
(“|third” worst)
C-d
(“|hird” worst)


paredit-forward-delete

(w |(x) y)

keys (w (|x) y)
C-d (w (|) y)

(w | y)

paredit-backward-delete

(w (x)| y)

keys (w (x|) y)
DEL (w (|) y)

(w | y)

paredit-kill

keys
(zee)| ;comment
C-k
(zee)|


paredit-kill

(|zee) ;comment

keys (|) ;comment
C-k
(println “|x is:” x)
(println “|” x)

paredit-forward-kill-word

|(declare x) ;comment
keys
(| x) ;comment
M-d
(|) ;comment
() ;|

paredit-forward-kill-word

;| hack
(declare x)
keys
;|
M-d (declare x)
;
(| x)

paredit-backward-kill-word

(declare x) ;comment
(zee) |
keys
(declare x) ;comment
M-DEL
(|)

(declare x) ;|

paredit-backward-kill-word

keys (declare x) ;|
M-DEL (declare |)
(|)


4/8 movement & navigation


paredit-forward

keys
(conj |[1 2 3] 4)
C-M-f
(conj [1 2 3]| 4)


paredit-forward

keys (conj [1 2 3] |4)
C-M-f (conj [1 2 3] 4|)
(conj [1 2 3] 4)|


paredit-backward

keys
(conj [1 2 3]| 4)
C-M-b
(conj |[1 2 3] 4)


paredit-backward

keys (conj| [1 2 3] 4)
C-M-b (|conj [1 2 3] 4)
|(conj [1 2 3] 4)


intermission

http://www.ﬂickr.com/photos/nickporjr/2158780350/

5/8 depth-changing commands


paredit-wrap-around

keys
(eat |cky bcn)
M-(
(eat (|cky) bcn)

same for {}, [], and “”


paredit-splice-sexp

keys
(eat (|cky bcn) sdwch)
M-s
(eat |cky bcn sdwch)


paredit-splice-sexp-killing-backward

keys
(eat (cky |bcn))
M-<up>
(eat |bcn)


paredit-splice-sexp-killing-forward

keys
(eat (cky |bcn))
M-<down>
(eat cky|)


paredit-raise-sexp

keys (eat (cky |bcn) sdwch)
M-r (eat |bcn sdwch)
|bcn


6/8 barfage & slurpage


paredit-forward-slurp-sexp

keys
(eat (|cky) bcn z)
C-)
C-<right> (eat (|cky bcn) z)


paredit-forward-barf-sexp

keys
(eat (|cky bcn) z)
C-}
C-<left> (eat (|cky) bcn z)


paredit-backward-slurp-sexp

keys
C-( (omg eat (|cky) bcn)
C-M-<left> (omg (eat |cky) bcn)


paredit-backward-barf-sexp

keys
C-{ (omg (eat |cky) bcn)
C-M-<right> (omg eat (|cky) bcn)


7/8 miscellaneous commands


paredit-split-sexp

keys
(cky |bcn)
M-S-s
(cky) |(bcn)



paredit-join-sexps
(cky)| (bcn)
(cky| bcn)
keys
chunky-
M-S-j | bacon
chunky-|bacon


intermission


8/8 in the wild
(tips and tricks)


C-w is not a paredit thing
show-paren-mode warning
8.1/8 demo ﬁxing unbalanced parens


add parens when unbalanced
(override matched keys w/ C-q)

keys (important |
C-q )
(important )|



remove pesky spaces

(important
| )
keys
(important
C-k
then |)
<del> (important |)

remove stray parens
with comments

poor paren)|
keys
poor paren|)
DEL
then ; then poor paren;|)
C-d poor paren;|

override paredit delete

keys
C-u DEL
C-u C-d LTR
C-u C-k

remove stray parens
probably the right way

keys
poor paren)|
C-u DEL
poor paren|


dammit, emacs

keys

M-x butterﬂy LTR


M-x butterﬂy

add paredit to the SLIME REPL

;; enable paredit in slime repl
(add-hook 'slime-repl-mode-hook (lambda () (paredit-mode +1)))

Karol Skocik - http://coding.derkeiler.com/Archive/Lisp/comp.lang.lisp/2007-07/

customize

;;; Customize paredit using èval-after-load':
;;;
;;; (eval-after-load 'paredit
;;; '(progn ...redefine keys, &c....))
;;;
;;; ... Now `)' is bound to a
;;; command that does not insert a newline, and `M-)' is bound to the
;;; command that inserts a newline. To revert to the former behaviour,
;;; add the following forms to an èval-after-load' form for paredit.el
;;; in your .emacs file:
;;;
;;; (define-key paredit-mode-map (kbd ")")
;;; 'paredit-close-round-and-newline)
;;; (define-key paredit-mode-map (kbd "M-)")
;;; 'paredit-close-round)

http://mumble.net/~campbell/emacs/paredit.el


http://www.emacswiki.org/emacs/PareditCheatsheet

stole from...

๏ http://mumble.net/~campbell/emacs/paredit.html
๏ http://p.hagelb.org/paredit-screencast.html
technomancy - screencast soon?


consume these...

๏ http://www.emacswiki.org/emacs/ParEdit
๏ http://steve.yegge.googlepages.com/effective-emacs
๏ Peepcode: Meet Emacs
๏ http://peepcode.com/products/meet-emacs

๏ Peepcode: Functional Programming with Clojure
๏ http://peepcode.com/products/functional-programming-with-clojure


images and food...
๏ Pretzels - http://www.flickr.com/photos/bellalago/3938498023/
๏ XKCD “Lisp Cycles” - http://xkcd.com/297/
๏ XKCD “Lisp” - http://xkcd.com/224/
๏ XKCD “Real Programmers” - http://xkcd.com/378/
๏ Obligatory LOLCAT - http://www.flickr.com/photos/nickporjr/2158780350/
๏ http://www.emacswiki.org/emacs/PareditCheatsheet
๏ thanks to runa, for the food

http://bitterfilms.shop.musictoday.com/Product.aspx?pc=8BCT06#

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