Type Less to Type More

Emacs has two modes,

when combined, these modes allow you to type half as much and produce twice as much code. An abbrev is a string of characters, that will be expanded to a longer string, skeletons on the other hand are templates written in a mini language, implemented in elisp. When an abbrev is set to expand into a skeleton, you can write chunks of code with just a few keystrokes.

One of the most frequent statements I use for debugging is the print call, instead of typing,

System.out.println(" some thing.. " );

every time, I can just type "prt" and when I hit space it will be expanded to the form above. For this we need to define a skeleton for it,

 (define-skeleton skel-java-println
   "Insert a Java println Statement"
   nil
   "System.out.println(" _ " );")

"_" denotes where the cursor will be placed after the expansion. Now to test this use M-x "skel-java-println"

System.out.println( );

it should insert the code and place the cursor inside the parenthesis. Using M-x is nice but it is still way to slow for our purposes, next we define a abbrev for java-mode,

(define-abbrev java-mode-abbrev-table "prt" "" 'skel-java-println)

Now every time we type "prt" in java-mode, it will be expanded to a print statement. Of course you are not limited to one liners,

 (define-skeleton skel-java-try
   "Insert a try catch block"
   nil
   \n >
   "try{"
   \n >
   _ \n
   "}catch( Exception e ) {" >
   " "
   \n > \n
   "}" >)

will expand to,

 try{

 }catch( Exception e ) { 

 }

here "\n" denotes a new line and ">" means the line will be indented, to match where you are in the code.

To activate abbrev-mode add,

(setq abbrev-mode t)

to your .emacs file, along with the skeletons. Now Emacs may complain as you load your .emacs file that some modes doesn't have abbrev tables, in that case define them before the skeleton definitions,

(define-abbrev-table 'java-mode-abbrev-table '())

If the mode doesn't have any abbrev table set, you also need to set the table for use in the mode this happened to me with clojure-mode,

 (add-hook 'clojure-mode-hook 
           (lambda ()
             (setq local-abbrev-table clojure-mode-abbrev-table)))

While at it, enable skeleton-pair mode,

 (setq skeleton-pair t)
 (global-set-key (kbd "(") 'skeleton-pair-insert-maybe)
 (global-set-key (kbd "[") 'skeleton-pair-insert-maybe)
 (global-set-key (kbd "{") 'skeleton-pair-insert-maybe)
 (global-set-key (kbd "\"") 'skeleton-pair-insert-maybe)

now every time you type [ ( " { , these will be inserted in pairs, one less thing to type.

Tags: emacs