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Comment by sevensor | Hacker News Reader

Vim is a great editor, and when I see people laboriously clicking to create multiple cursors to do something that a simple s/foo/bar/g would accomplish, I feel sorry for them. However, multiple cursors can be pretty great; I love the implementation in kakoune, where I can make multiple selections and then replace them with the output of piping them through an arbitrary shell command. I like to do this with basic math I write out as inputs to dc and then transform to the computed results using select and pipe.

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Would s/foo/bar/g change every foo into bar without also changing every food into bard?

Also in most use cases, clicking for each multicursor is the wrong way to do it.

With multicursor you can:

- Press a shortcut to auto select every instance of the characters that you already have highlighted (which is just s/foo/bar/g with visual feedback before confirming)

- Press your "select next occurrence" shortcut a few times so you're only changing the first few occurrences that you care about.

- Press your "select next occurrence" shortcut to select the instances you want and press your "skip next occurrence" shortcut to skip the instances you want to keep. That way you can change a bunch of "foo"s to "bar"s while keeping all "food"s as "food"s but also keeping those few instances of "foo" that you want to stay as "foo" (such as in comments, imports, tests, etc...)

- Press your "select next occurrence" shortcut (usually ctrl/cmd + d) each time if you literally want to see each instance before moving on to the next. Usually this is when you really want to make sure of something next to one of the occurrences.

- And finally clicking each cursor if there really is no simple pre-existing pattern for where you're trying to make changes

In vim, you can do s/foo/bar/gc to iteratively confirm or skip each replacement.

> Would s/foo/bar/g change every foo into bar without also changing every food into bard?

Sure, and if that’s the case you write a better pattern. The replacement s/foo/bar/g applies only to the current line as written. It’s easy to see if it will work or not. But if you also have food on the same line, you can write s/foo\ze\W/bar/g to match foo followed by a non-letter and replace only foo.

> Also in most use cases, clicking for each multicursor is the wrong way to do it.

Maybe, but I’ve sure spent a lot of time pair programming with people who do it, which is why I bring it up. For what it’s worth, I prefer multicursors, and my find-and-replace workflow is much as you describe, albeit entirely keyboard and regex driven. Your average junior programmer who just learned vscode three or four years ago only knows multiclicking though, and I don’t want to kill the momentum by interrupting to point out how they could use their tools better.

I use multiple cursors all the time and rarely use the mouse to create them. Either it's "Add cursor to line ends" (VSCode)/"Split into lines"(Sublime) or just Ctrl+D.

I use Vim every day, but sometimes it's simply more convenient to visually confirm how something should be aligned etc., which is where Visual Block mode comes in handy. And Visual Block mode is just multiple cursors limited to a single column, so I can definitely see how multi-cursor support can be a more modern evolution.

Can you give an example of using dc like this? Seems like something I would find really useful!

Absolutely!

Suppose I'm editing a text file, and I'm working through a tradeoff between data volume and accuracy, where more accuracy requires more data. I have an array of 14 sensors, and I can configure them to take either 100-byte samples or 500-byte samples, and I can take samples at intervals between 1 and 60 seconds.

So I make myself a little table:

    sensors size interval
    14      100  1
    14      100  30
    14      100  60

Then I duplicate it:

    sensors size interval
    14      100  1
    14      100  30
    14      100  60
    14      100  1
    14      100  30
    14      100  60

I'm using kakoune, so I can put my cursor on the 100 in the first duplicate row, press C twice, then press r5, and now I have this table:

    sensors size interval
    14      100  1
    14      100  30
    14      100  60
    14      500  1
    14      500  30
    14      500  60

Now, I want to know bytes per day, and this is where the math comes in. I start adding columns. First I duplicate the three existing columns, since I want to see them next to the result. I can do this by putting a cursor at the beginning of each row, highlighting the whole thing, and pasting. I also hit & to line up the pasted selections.

    sensors size interval
    14      100  1        14      100  1       
    14      100  30       14      100  30      
    14      100  60       14      100  60      
    14      500  1        14      500  1       
    14      500  30       14      500  30      
    14      500  60       14      500  60

Now, because I don't want to have to think about the stack too hard, I put 1440 (minutes per day) and 60 (seconds per minute) in before the interval column.

    sensors size interval
    14      100  1        14      100  1440 60 1       
    14      100  30       14      100  1440 60 30      
    14      100  60       14      100  1440 60 60      
    14      500  1        14      500  1440 60 1       
    14      500  30       14      500  1440 60 30      
    14      500  60       14      500  1440 60 60

Then I add my operations. And keep in mind I'm still using multiple cursors, so all this stuff is just getting typed one time.

    sensors size interval
    14      100  1        14      100  * 1440 * 60 * 1 / p      
    14      100  30       14      100  * 1440 * 60 * 30 / p     
    14      100  60       14      100  * 1440 * 60 * 60 / p     
    14      500  1        14      500  * 1440 * 60 * 1 / p      
    14      500  30       14      500  * 1440 * 60 * 30 / p     
    14      500  60       14      500  * 1440 * 60 * 60 / p

Now each line has a little dc program on it, like 14 500 * 1440 * 60 * 60 / p.

I then highlight the back half of each row (again, still working with the same set of cursors the whole time, it takes way longer to explain this than it does to actually do it.) I type

    | dc

and each of my selections gets run through dc. The result is:

    sensors size interval
    14      100  1        120960000
    14      100  30       4032000
    14      100  60       2016000
    14      500  1        604800000
    14      500  30       20160000
    14      500  60       10080000

That's not super readable, so I cursor over three times (multiselection is still active!) and insert commas, and then I do it again:

    sensors size interval
    14      100  1        120,960,000
    14      100  30       4,032,000
    14      100  60       2,016,000
    14      500  1        604,800,000
    14      500  30       20,160,000
    14      500  60       10,080,000

The result is I've done a quick back-of-the-envelope calculation on how much data I need to handle in each scenario.

Replying to my own post for a couple of follow on comments:

1. I wrote this comment using kakoune as the editor under w3m

2. I don’t know emacs as well as I’d like to. Anyone want to chime in on how you’d do this in emacs?

Thanks! This is pretty cool. I do often run shell commands on entire lines/ranges of lines in vim, but haven't tried it with just parts of lines. I just tried with vim's rectangular selection, and while it does correctly give the 'dc' output, it replaces entire lines with the output instead of just the selection. I'll have to look into this further.

Enjoy! Kakoune’s selection-verb editing model really clicked for me; I had been a heavy user of visual mode in vim before I switched. The great Unix integration composes really well with the selection model too.

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