Vim Macro on Every Line of Visual Selection

Question

I'd like to run a macro on every line in a selection, rather than totalling up the number of lines in my head. For instance, I might write a macro to transform:

Last, First

Into

First Last

and I'd like it to run on all these lines:

Stewart, John 
Pumpkin, Freddy
Mai, Stefan
...

Any ideas Vim gurus?

EDIT: This is just an example, obviously this is trivialy regexable, but there are other instances that come up that aren't quite so easy that I'd prefer to use macros.

Answer 1

Suppose you had a macro q that ran (and remained) on a single line. Then you could run it on every line in your selection with:

:'<,'>normal @q

(if you already have a group of lines selected, hitting : produces :'<,'> on the command line)

For example, the following macro capitalizes every word but the first on a line:

:let @q="^dwgU$P"

So running it on the following (where the + lines are selected)

 0000: a long long time ago
 0001: in a galaxy far away
+0002: naboo was under an attack
+0003: and i thought me and qui-gon jinn
+0004: could talk the federation in
 0005: to maybe cutting them a little slack.

With the above normal @q command, produces:

 0000: a long long time ago
 0001: in a galaxy far away
 0002: naboo WAS UNDER AN ATTACK
 0003: and I THOUGHT ME AND QUI-GON JINN
 0004: could TALK THE FEDERATION IN
 0005: to maybe cutting them a little slack.