Stop the Vertical Tab Madness (2010)

http://prog21.dadgum.com/76.html

by draegtun • 11 years ago

85 63 11 years ago

prog21.dadgum.com

VeejayRampay• 11 years ago

Used to be a way to detect IE back in the days.

http://ajaxian.com/archives/ievv

GrantSolar• 11 years ago

Ironically, this is the first time I've heard of `\v`

agumonkey7• 11 years ago

Old codes are full of gems. ASCII has field record separator for instance. Free CSV.

wglb2• 11 years ago

Oh, would that we had used that to begin with instead of the ghastly quote convention!

simonbyrne• 11 years ago

I wonder why these are no longer used. There is the obvious visibility issue, but tab delimited files are still quite common. I wonder if it was because languages (particularly C, and all languages which copy the C convention) don't provide escape characters for them?

jug• 11 years ago

Reading https://en.wikipedia.org/wiki/C0_and_C1_control_codes now and getting this urge to write a pure ASCII editor, haha.. Seriously, it's actually suitable for more advanced editing than modern day "pure text" editors.

SOH + STX to set a document title. FF for page breaks. DLE to allow embedded (binary/uninterpreted) data like images and avoid printing garbage. FS, GS, RS, US to support tables.

I find it interesting that this coincidentally works complementary to syntax like Markdown. :p

userbinator2• 11 years ago

From https://en.wikipedia.org/wiki/Tab_key :

"In practice, settable tab stops were rather quickly replaced with fixed tab stops, de facto standardized at every multiple of 8 characters horizontally, and every 6 lines vertically (typically one inch vertically)."

You could try testing this.

As for removing it, I'm not convinced that it's worth the effort to; it's basically a single case in an escape-handling switch. The article he links to in the first line can basically be summarised as "I don't understand escaping and want to replace it with something even more complex".

billforsternz2• 11 years ago

I think the article he links to can basically be summarised as "Escaping considered harmful, here's a better way to solve the same problem". I don't see any evidence that he doesn't understand escaping, and his claim that eliminating it would be a net win seems plausible (at least) to me.

userbinator2• 11 years ago

I don't think what he proposes is really a better way, because requiring compilers to comprehend string concatenation and a few more extra reserved words specifically for the characters is a more complex and less general solution than encoding using the string itself, which is what escaping does.

Escaping is amazingly elegant once you realise how general and simple it is, and it's also very important to understand it when designing things like data formats and protocols (length-delimited fields are the best, but it is not always possible.) Ignoring escaping, which is what would otherwise occur, tends to cause rather horrible security issues.

Swizec• 11 years ago

For what it's worth, I've never before heard of \v.

oneandoneis2• 11 years ago

Perl staying ahead of the curve as usual ;)

tom-lord• 11 years ago

If I could stealthily patch the compiler for any language supporting the "\v" escape so I'd receive mail whenever it occurred in source code, then I could trace actual uses of it. I'm willing to bet that all the mail would come from beginners trying to figure out what the heck "\v" actually does, and then giving up when they realize it doesn't do anything.

Whilst it's true that I've never actually used `\v`, I have included it in code before to cover genuine, necessary edge cases... For example:

https://github.com/tom-lord/regexp-examples/blob/master/lib/...

kriro• 11 years ago

The contrarian in me wants to update slide #1 to

>> print('Hello,\vworld!');

now :D

Actually I think I'll include a "guess what this control sequence does" slide before discussing them.

jkire• 11 years ago

Here's my simple plea: stop it. Stop mentioning vertical tabs in tutorials and language references.

I'm failing to see why this is an issue? The examples tutorials/references he gave only mention '\v' in tables of possible escapes. What is the downside to mentioning it, people spending 5 minutes googling for what a vertical tab is?

Unless a language removes support for escaped string literals entirely it seems odd to remove support for a particular standard, if mostly unused, escape sequence.

zaphar• 11 years ago

When I was a very green coder I saw the vertical tab in one of those tables and spent a fruitless afternoon trying to use it to align some text. I don't even remember what I thought it did but the afternoon could have been better spent if anything anywhere had said it does absolutely nothing on any modern system.

So the harm is that people see vertical tab and without the associated historical context come up with their own ideas of what it does and then waste time.

If you do include it at least show it in such a way that people know it's a historical oddity with really nothing but very obscure uses like the fingerprinting example mentioned elsewhere in the comments.

chjj• 11 years ago

Is \v being mentioned in specifications really causing a problem? I've never seen someone mistakenly use a vertical tab in code where they could be using something better.

Maybe it's useless, but I wouldn't say it's harmful. This is a pretty overzealous rant over nothing: it's almost as useless as the vertical tab.

1wd2• 11 years ago

Random fact: Microsoft PowerPoint inserts a vertical tab when you press Shift+Enter, e.g. to start a new line inside the current bullet point.

err4nt• 11 years ago

I always understood this functionality as 'soft return' versus a 'hard return'. One adding a line break (like <br> in HTML) and the other starting a new paragraph (like <p>) with its own indent/margin/spacing rules.

chias• 11 years ago

Is that a vertical tab, or a line break? It seems much more consistent with the behavior of <br> in HTML documents (i.e. new line but not new paragraph/bullet/whatever).

JonathonW• 11 years ago

In the XML PowerPoint format (.pptx), it's a line break (inserts an <a:br> element between the two lines). There's no vertical tab character saved out to disk (who knows what PowerPoint does internally, though).

I don't have the time or the initiative to figure out what the old .ppt format does here.

unwind• 11 years ago

That's a part of the GNU Coding Standards which say:

Please use formfeed characters (control-L) to divide the program into pages at logical places (but not within a function)..

I always found that particularly archaic.

And yes, of course I realize that vertical tab and form feed are distinct characters.

froydnj• 11 years ago

Obviously it's helpful for printing things.

Less obviously, emacs has commands that navigate by logical pages (C-x [, C-x ]). And of course you can adjust the regex that denotes logical pages.

wtbob• 11 years ago

^L is supported in most pagers and news clients to split pause scrolling, so this makes sense.

billyhoffman• 11 years ago

I've used \v support, or lack there of, to fingerprint web devices during security audits.

Whitespace is often defined as space, \t, \r, \n, and \v. However many specs, like HTTP, will sometimes exclude \v. Depending on the underline functions products use in their HTTP parsers, you can fingerprint servers, WAFs, proxies, load balancers, whatever when using \v to separate HTTP headers lines or name\value pairs

KeytarHero3• 11 years ago

    name
        alue

pairs? ;)

bjourne• 11 years ago

What's the harm? In any software project useless shit accumulate because it is much easier to add features than to remove them. Support for one useless feature such as \v will not make a codebase into a mess of spaghetti, but support for enough useless features like \v absolutely will.

The burden for \v is not zero. Every programmer working on the string escapes part of the code has to read and understand the lines that implement it. And it has to be tested and documented and if your documentation comes in multiple languages, translators have to spend time translating text for a completely useless feature.

Writing software is like writing a book of code for other programmers to read. An author wouldn't leave in meaningless chapters in the book it is writing because "what's the harm?" and neither should good programmers.

couchand• 11 years ago

While your argument holds generally, let's remember that unless the software is horribly architected the difference between escape-everything-but-vertical-tab and escape-everything really should be trivial.

franciscop• 11 years ago

I am surprised that no one has commented on vertical languages. I am learning Japanese and I can see how this would be really useful in any vertical writing languages.

halosghost• 11 years ago

Actually, glibc's argp library (a more featureful alternative to getopt) uses '\v' for a few things (though, not at all for what it is normally used to mean :P).

muchcomment• 11 years ago

Had my first encounter with \v doing an import of a legacy database just a few weeks ago. The data was passed on to us in a batch of XML-files. For some reason our XML parsing library would just ignore the rest of the file when it came to the \v character. Took me some time to find the culprit.

Edit: The \v character had somehow made it into one of the descriptions for one of the user profiles.

jerf2• 11 years ago

Just checked, and \v is illegal in the characters of an XML document: http://www.w3.org/TR/REC-xml/#dt-text

But you should have gotten an error, of course, not the silent truncation you imply.

If you need to salvage the character, your XML library may let you specify it as &#0b;. That is still a violation, but a lot of libraries seem to let it through: http://www.w3.org/TR/REC-xml/#sec-references (see "Well-formedness constraint"... you are specifically not allowed to use this to do what I'm suggesting here).

Anyways, the moral here is that XML CAN NOT carry arbitrary binary, and EVERY TIME you output something in XML, something in the system needs to run some sort of encoding & illegal-character cleaning pass on the output text. The moral equivalent of "<tag>$content</tag>" in your language is ALWAYS wrong, unless you specifically processed $content into XML character content earlier. This is true even when your really sure $content is "safe". Even if you're right... and statistically speaking, you're not... do it correctly anyhow and call the right encoding function.

spdustin• 11 years ago

I've dealt with vertical tabs and linefeeds by just Base64-encoding character data that might include them before stuffing it into a CDATA node in the XML doc.

It's a hack, sure, having to encode/decode all the time, but if you need to store those characters, it's the only bulletproof way I've found.

lubujackson• 11 years ago

\v makes a better separating character than commas or tabs since it won't appear naturally in text.

kevin_thibedeau• 11 years ago

RS is even better since it's, you know, the record separator.

1_player• 11 years ago

There was a Python web framework which used \v to separate between code and HTML.. Does any of you remember the name?

EDIT: found it, it's called Aspen (http://aspen.io/simplates/). They actually were using form feed (^L or \f), but apparently have switched to an ASCII combination to separate code from presentation.

From the web archive: https://web.archive.org/web/20110412072653/http://aspen.io/p...

There's an old HN discussion about it: https://news.ycombinator.com/item?id=2410221

zimbu668• 11 years ago

After we remove support for vertical tab can we drop octal literals from every language? As fun as it is to snicker at a young programmer who spent 2 hours debugging

x = 0123

it's time for octal to go away.

desdiv• 11 years ago

Hear, hear.

Scala recently removed it altogether: https://issues.scala-lang.org/browse/SI-5205

Other languages (Python 3, Ruby) are moving to the 0o syntax.

pekk• 11 years ago

Python has had octal literals like this for years, so it is misleading to say that it is "moving to" it.

KeytarHero3• 11 years ago

Same with trigraphs - as much fun as it is to joke about the ??!??! operator[0]

[0] http://stackoverflow.com/questions/7825055/what-does-the-c-o...

GFK_of_xmaspast• 11 years ago

I think trigraphs are supposed to be going away in c++17.

jrochkind12• 11 years ago

There are often use cases for many of the ASCII control characters, which is why the escape sequence feature is there.

It would be odd to support an escape sequence feature for every ASCII control character _except_ vertical tab, or to support it but leave it out of the docs.

It's just coming along for the ride with the general escape sequences for ASCII control chars features.

sophacles• 11 years ago

Just for fun, I decided to see what the heck '\v' does....

   >>> print 'hello\vworld'
   hello
        world
   >>> print 'hello\v\vworld'
   hello

        world

Now I want to use it a bunch.

Stop the Vertical Tab Madness (2010)

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