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DépartementOffice

Emacs, a performant IDE for Perl

Tutorial for YAPC.:EU:::2009, Lisbon

laurent.dami@justice.ge.ch

DépartementOffice

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Overview

• Intended audience– Emacs newcomers– [ seasoned Emacs users … may find some additional tips ]– curious …

• Topics– Intro– Emacs concepts– General editing– Perl programming– External tools– Emacs-Perl integration : extension packages

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What is Emacs ?

• "Emacs is the extensible, customizable, self-documenting real-time display editor".

– advanced : provides much more than simple insertion and deletion. It can control subprocesses, indent programs automatically, show two or more files at once, and edit formatted text.

– self-documenting : can type C-h at any time to find out what the options are.

– customizable : thousands of variables – extensible : internal Lisp interpreter– feature-rich : thousands of commands

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Emacs history

• early 1970s : initial work on PDP computers (MIT Labs)

• 1976 : first release• 1981 : Gosling Emacs on Unix• 1986 : GNU Emacs 15.34• 1991 : XEmacs fork (formerly Lucid Emacs)• 2008: GNU Emacs 22.3

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Emacs main concepts

• buffer : basic editing unit (text being edited). Can be bound to various contents like :– file (local/remote)– computed content (listings, compilation results, shell, email, etc.)– external process

• window : screen area for displaying buffer content• frame : OS window• mode : set of options for editing some kind of content

– major mode : mutually exclusive– minor mode : additional options (plugin)

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Other concepts

• region : portion of buffer between mark and point

• rectangle : rectangular area instead of linear text

• register : memory for storing text / position / rectangle

• macro : recorded sequence of keys• desktop : saved Emacs session

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User input

• Input events– character events– modifiers : <CTRL>, <ALT>, <META>, <SUPER>– mouse, scroll, click, focus, etc.

• Key sequence– prefix key keymap. Ex:

• C-x General extended commands• C-h Help commands• C-c Mode-specific extended commands

– complete key command

• Keymap– binding key command– global / local

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Entering commands/args in minibuffer

• Auto-completion• Default argument• Editing (cut/paste/move/etc.)• Command history

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Modes may implement …

• additional commands• local implementation for generic operations

– ex: comment-region, indent-region

• syntax highlighting• local keymaps• local menus• modifications to the display (ex. status line)• hooks

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Editing

• Move– by character, word, sentence, paragraph, page

• Copy / Cut / Paste– kill ring : history of killed fragments

• Search / Replace– incremental / regex– word search (without regard to punctuation)– clever case substitutions– recursive edit

• Abbrevs• Undo

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Files

• File names / completion / disambiguation• Remote files (ange-ftp / tramp)• Archives / compressed files• Mode chosen automatically from name or

content• Bookmarks (filename / position / comment)• Shadowing (automatic replication)• Filesets

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Editing directories

• listing• create / rename / delete• bulk operations (mark / regexp )• open subdirectories in same buffer• chmod, mkdir, etc.• exec shell command on file(s)

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Shell

• Inferior process– filename completion– history ring– editing command-line– directory tracking– remote host (telnet, rlogin, etc)

• Eshell – no process, all done in Emacs

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Help

• Info (manual)• Help on

– variables– functions– keys– bindings– mode– apropos

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Programming modes : generic features

• Recognize top-level definitions– go to begin / end, set region

(C-M-h), imenu

• Indentation– clever syntax parsing; various

indent styles (K&R, BSD, Gnu, etc.)

• Balanced parentheses– begin / end, up / down, kill,

• (C-M-LEFT, C-M-UP, ..)– blink-matching

• Comments– insert, realign, comment /

uncomment region, reformat

• Syntax highlighing

• Restricting editing scope– hideshow minor mode– narrowing

• (C-x n d / w)

• Autocompletion

• Electric characters– automatic reindent / newline

• Tags support

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Cperl mode

• based on C-mode– indenting– electric parentheses– automatic expansion (if, else, while, do, foreach, …)– syntax highlighting– binding to perlinfo– menu, tools– perldb : gud bindings

• next / step• break (C-x SP)

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Compiling and testing

• Compilation– launch compiler subprocess ("perl", "gcc", "make", etc.)– mod-compile.el : additional layer

• adapt compilation command to current language / context

– parse errors and navigate to source files– usual Emacs commands for viewing results / debug logs

• GUD (Grand Unified Debugger)– shell buffer– navigate to source files

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Searching

• builtin support for "grep"• ack.el : adaptation for "ack"• navigate in matched files like for the compilation

buffer

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Autocompletion

• Static sources– Tags– Language-specific doc

• More context-aware– Emacs extensions : Sepia, PerlySense

• Dabbrev– most recent, preceding word for which this is a prefix– if none, search following words– if none, search other "friend" buffers

• Hippie-expand– ring of try functions

• try-complete-file-name• try-expand-all-abbrevs• try-expand-line• try-expand-dabbrev• try-expand-whole-kill

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External filters

• Ex: perltidy

; tidy perl code on region(defun perltidy () "run perltidy on the current region or buffer." (interactive) (shell-command-on-region (point) (mark)

"perltidy -q" nil t))

(global-set-key "\C-ct" 'perltidy)

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Version control

• generic version control (VC)• psvn.el : SVN support

– status • dired-like

– log– ediff

• similar modes for git

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Differences / patches

• ediff-mode– both versions side-by-side (horizontal or vertical)– ediff commands

• previous / next• copy A B / B A

– apply patches (multifiles OK)

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perlcritic

• mode perlcritic.el distributed with Perl::Critic– apply on buffer– apply on region– parse output

• other solution: treat as a standard compile command– must configure .perlcriticrc so that Emacs understands

filenames

verbose = %f:%l:%c: %m, %e (%p, severity %s)\n

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Emacs::EPL

• Perl-Emacs IPC integration, followup to "Perlmacs"• looks like this was very nice work

– adapted environment for running Perl under Emacs• redefine STDIN, STDOUT as hooks to Emacs minibuffer• populate ENV• …

– can write Emacs modules in Perl instead of elisp !

• last distribution dates back to 2001, using Perl 5.004

• couldn't get it to work

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Devel::PerlySense

• Perl process in the background• Lots of features

– links to doc– class hierarchy analysis and method analysis– jump to definition / class– run / debug– run tests– interact with ack– notion of "project"– file templates

• but very CPU-intensive and slow

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Sepia

• last distrib May 09• Inspired by Emacs Lisp dev. philosophy• Features

– completion on partial words, i.e. L:U List::Util– inferior Perl process with REPL loop– analyses opcodes– links to doc, to func definitions, to modules

only recognizes core modules/functions– didn't figure how to let it read perl/site/lib !

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Emacs::PDE

• last distrib July 2008• Features (pde-load)

– projects– smart compile (C-c r) / debug– tags / menus / tree view (C-c C-v TAB)– perldoc integration with browser (C-c C-v RET, C-c C-v C-p)– special indenting mode– integrate with perltidy / perlcritic– interactive perl shell

no install problems• need to learn more