[Emacs] Fun with rectangles

Lets have some fun with emacs rectangles. Lets assume you have the following text:

012345678901234567890123456789
      val1 = 10;
      val2 = 20;
      val3 = 30;

Now, you need to add "(int)" in front of all the numbers. You can do it one line at a time, or you could use rectangles in emacs. Move the cursor to the start of 10, set mark, make the selection until start of 30. Hint: To set the mark, just hit Ctrl+Space and take your cursor to where you need to stop. Something like this,

012345678901234567890123456789
      val1 = 10;
      val2 = 20;
      val3 = 30;

Ok, now lets insert the string using "string-insert-rectangle" and enter the string that we want to be inserted, in our case "(int)"

M-x string-insert-rectangle
String insert rectangle (default void ): (int)

012345678901234567890123456789
      val1 = (int)10;
      val2 = (int)20;
      val3 = (int)30;

Now, say you wanted to give a space between the (int) and the number. Mark the rectangle as show below:

012345678901234567890123456789
      val1 = (int)10;
      val2 = (int)20;
      val3 = (int)30;

We will use the "open-rectangle" command now.

M-x open-rectangle

012345678901234567890123456789
      val1 = (int) 10;
      val2 = (int) 20;
      val3 = (int) 30;

Cool, now let's delete the spaces in the front using "delete-rectangle". Make the rectangle and...

012345678901234567890123456789
      val1 = (int) 10;
      val2 = (int) 20;
      val3 = (int) 30;

M-x delete-rectangle

012345678901234567890123456789
val1 = (int) 10;
val2 = (int) 20;
val3 = (int) 30;

Now, just for fun, we are going to cut a rectangle and yank it somewhere else. Lets remove 1,2,3 from the variable names and put them in the front (bad idea, I know). Lets select the rectangle and call the "kill-rectangle" command

012345678901234567890123456789
val1 = (int) 10;
val2 = (int) 20;
val3 = (int) 30;

M-x kill-rectangle

 012345678901234567890123456789
|val = (int) 10;
 val = (int) 20;
 val = (int) 30;

Move the cursor (show above as | ) to where you want to yank the rectangle now (in our case, the beginning of the word) and run "yank-rectangle"

M-x yank-rectangle

012345678901234567890123456789
1val = (int) 10;
2val = (int) 20;
3val = (int) 30;

Now, of course there are key-binding available (its Emacs for heaven's sake, even if there is no key-binding you can make your own).

From the Emacs manual

C-x r k

Kill the text of the region-rectangle, saving its contents as the “last killed rectangle” (kill-rectangle).

C-x r d

Delete the text of the region-rectangle (delete-rectangle).

C-x r y

Yank the last killed rectangle with its upper left corner at point (yank-rectangle).

C-x r o

Insert blank space to fill the space of the region-rectangle (open-rectangle). This pushes the previous contents of the region-rectangle to the right.

C-x r N

Insert line numbers along the left edge of the region-rectangle (rectangle-number-lines). This pushes the previous contents of the region-rectangle to the right.

C-x r c

Clear the region-rectangle by replacing all of its contents with spaces (clear-rectangle).

M-x delete-whitespace-rectangle

Delete whitespace in each of the lines on the specified rectangle, starting from the left edge column of the rectangle.

C-x r t string

Replace rectangle contents with string on each line (string-rectangle).

M-x string-insert-rectangle string

Insert string on each line of the rectangle.

Enjoy!