Ivo – a reimagined Unix terminal system
lubutu.com
lubutu.com
A UNIX wizard hears cries of torment from his apprentice's computer room where the apprentice is studying, and goes to investigate.
He finds the apprentice in obvious distress, nearly on the verge of tears. "What's the problem?" he asks. "Why did you cry out?"
"It's terrible using this system. I must use four editors each day to get my studies done, because not one of them does everything."
The wizard nods sagely, and asks, "And what would you propose that will solve this obvious dilemma?"
The student thinks carefully for several minutes, and his face then lights up in delight. Excitedly, he says, "Well, it's obvious. I will write the best editor ever. It will do everything that the existing four editors do, but do their jobs better, and faster. And because of my new editor, the world will be a better place."
The wizard quickly raises his hand and smacks the apprentice on the side of his head. The wizard is old and frail, and the apprentice isn't physically hurt, but is shocked by what has happened. He turns his head to face the wizard. "What have I done wrong?" he asks.
"Fool!" says the wizard. "Do you think I want to learn yet another editor?"
Immediately, the apprentice is enlightened.
Bourne, ash, bash, dash, ksh, mksh, zsh, csh, tcsh, rc, GNU Screen, etc, Each of them has a slightly different featureset. You can go with the default of bash and it could work out very well for you, but you'd be turning down potentially better alternatives. You seem pretty derisive towards hobbyist projects for a site called "Hacker News". That hobbyist project could be the best thing you've ever used, but you'll never know. That was the entire point of my original post.
Scrutinizing an idea for a new method of programmer-computer interaction from the perspective of a newcomer makes little sense to me, as does the "competing standards" thing from a neighboring comment, scrutinizing OP's idea for being potentially unable to win a popularity contest. OP's terminal system isn't a standard struggling to gain widespread public acceptance. It's just some guy's program.
I think that an idea about programmer-computer interaction ought to be scrutinized for its merit in facilitating programmer-computer interaction, and that criticism from a perspective that isn't the programmer's and isn't the computer's is useless.
PS. You forgot one of the most interesting Unix shells, es. It could turn out to be the best shell you've ever used.
Citation needed :)
Hacker News certainly wouldn't exist. The web wouldn't exist.
Hell, Unix wouldn't have ever existed.
Yeah, how dumb and harmful that is, asking people to think before acting.
Storing code as pure structure (not XML or anything silly, the serialization is trivial) avoids a huge class of artificial problems we've had to deal with since the dawn of compilers, due to the disconnect between human meaning encoded in plaintext and machine parsing.
Visualizing code as text--text as the primary view in the MVC, complemented with colours and annotations and hyperlinks and hints--is extremely useful. What we really need is a structural editor with the familiarity and ease of use of a text editor. But that is a hard problem, and more polished text manipulators are a nice stop-gap in the meanwhile.
s-expressions, then. High-end Lisp editors can do a good bit of structural editing based on the fact s-expressions are pure structure.
> The gap between the goal-completion logic a user comes up with and how they turn those mental instructions into plaintext is an unnecessary jump--an encoding--that produces no end of trivial but infuriating miscommunications.
I think this is the wrong idea. Coming up with the logic in the first place is the hard part; encoding it is trivial once the encoding is learned. The fact is, thinking logically long enough to come up with a nontrivial piece of logic for a computer to execute is hard for humans, as is turning that logic, in whatever form it's stored, into an intuitive mental structure.
> I think this is the wrong idea [...]
You're arguing about something else. I worded it badly. The logic is hard and the transformation into a series of instructions is hard. Once you're about to type those in, though, you should be having a conversation with the computer, as opposed to sending a series of tokens into a black box and wondering if it understood what you meant.
And in Smalltalk, applications lived in the image and were difficult to extract from it. They didn't work well with code outside the image.
That was a bigger deal when the Desktop was King. It might actually be an advantage for web applications: Everything in the image is trusted in your security model and nothing much from the outside can get in. Run the image in a virtual machine (think Xen) to enhance the iron box effect.
> Code stored like git stores data, with hashes and version control.
I don't... we already have git. What could be more 'like git' than git?
> Once you're about to type those in, though, you should be having a conversation with the computer, as opposed to sending a series of tokens into a black box and wondering if it understood what you meant.
There has been some slight work done towards visual development, where you create 'circuit-diagram software': wire up logical components with visual control flow (or visual data flow, perhaps). It never seems to catch on.
We've done this in the past. You can blame implementation, perhaps, but we've found that in our use case (3D graphics processing workflows), it starts to get too hard to understand what is occuring for any non-trivial "program", since you're bound by the constraints of how much information we decided to display visually, whereas with a general purpose domain-specific programming language you can choose how much information to surface, by being able to choose the level of abstraction you want (or not, as the case may be).
The reason we chose to go visually in the first place, is because someone has the bright idea that "anyone" should be able to create these workflows, but it ends up that a technically minded 3D graphics engineer does it anyway, and they just get frustrated by not being able to write a proper program/script :)
Think of code where every blob in the git DAG is one AST node. (Obviously this is horrendously inefficient, this is just an example.) No plaintext.
I'm not talking about that particular subset of visual systems like circuit diagrams or other awkward things like LEGO mindstorms. A good representation would still look like code as you know it, since that's proved to be such an information-dense and useful form. The "view" is the same, but the model has been separated from it.
Yes, the idea is to unify the structure editor with version control. Having the entire history of how nodes were moved around in the code gives you perfect knowledge of what was moved where or changed into something else, unlike line-based editing, where the problem is AI-complete.
When I'm working with Lisp in Emacs using Paredit, I am not editing text. Instead it is an interface to the expressions directly. I add, remove, transpose, cut, paste, move around, up and down, all with whole expressions at a time.
If someone were to build a new structural editor for programs, I could only hope it is as good as Paredit.
The problems with Lisp are that your source code ends up flattened into plaintext in the end, and that identifiers and symbols must be resolved by string lookup; there is no "first-class" reference, just a collection of resolution rules and environments and symbol manglers. You could fix these, but you wouldn't really have Lisp anymore.
I love Emacs too, but so far I've managed to constrain myself to caressing it only with my fingers.
If what I'm editing is not the original data, it had best be a perfect, 1:1 representation of that data; I should be able to edit any part of it with a regex without the fear of losing data or missing some annotation I can't see. Certainly in the case of an editor designed for programmers, that will mostly be true-- but there's a good chance that it won't be completely true, and then suddenly the editor is getting in my way and wasting my time.
I don't want to fight against technology. With current editors, I can get pretty much the same functionality, but all the metadata required to colorize text, tab complete, jump to definition, refactor, navigate by s-expr, etc. is just a cache, not something I have to think about.
p.s. this is why I hate Xcode project files.
In following the links to the paper on Femke, I found in that paper this expansion of the acronym Femke: "emphfunctional micro kernel experiment". I had to look at it a while before I realized that the markup had leaked into the result.
Then I though that "emphfunctional" might just be a very useful neologism, perhaps one that well describes the primary article's idealistic shell, but I'm not sure what it should mean yet.
These are the questions that plague the mind that is having trouble focusing on its work.
If you've got something better in mind, let's see it. I mean, let's see exactly how it is supposed to work. The general idea has been around a long time, but nobody has produced even a design that is compelling.
This reminded me of NASA 'Mission Control' used for Apollo.
To eyes used to the movies or video games the consoles look bizarre: there are no graphs, no icons, no _pictures_. All the data came in, and went out, as numbers, or text.
They did it like that because to the engineers on the console the numbers could be grasped more quickly and meant more than a picture.
One thing stands out in my mind: the guys on the console for Apollo were not the same guys on the console in 1986.
Was the problem the way the data was presented, the people interpreting the data, or an organizational problem?
Also, some parts of the proposal are very vague (description of MVC), while others are extremely specific (whole paragraph about an obscure Unicode delimiter), which makes it hard to get the big picture. That said, improving the terminal is a really challenging and important problem, so I'm glad there are people thinking about it.
People thought about it 20 years ago, not only about the terminal, but about improving UNIX in general. And not just any people, but the people that did UNIX and C in the first place. Their effort is called Plan9.
Very few people have heard of Plan9 and of those people even fewer used it to the point of understanding the novel ideas.
I use it. Even when I am forced to use UNIX I still use the Plan9 tools along with the Acme and Sam editors. Once you get used to the new Plan9 ideas, you feel crippled in UNIX and can never go back.
Would you care to expand on this? Any specific examples of things that Plan9 does for you that you feel crippled without? I ask out of genuine curiousity, as I've often heard Plan9 mentioned but have never given it enough research to understand its appeal.
For example, I'm a full time web developer and I spent a lot of time in zsh and vim. Would you recommend that someone like me checks out Plan9? Is it the type of thing you could possibly use as your general purpose OS?
Aside of that there's a big chunk of remote filesystem access ported from Plan 9, but I haven't used that yet.
Acme is, in fact, a modern, windowing terminal -- it lets you view, edit, execute and navigate. No surprise given that it comes from Rob Pike -- one of the guys behind an earlier windowing terminal: http://en.wikipedia.org/wiki/Blit_(computer_terminal) http://doc.cat-v.org/bell_labs/blit/
http://swtch.com/plan9port/ is quite easy to start with on any POSIX system.
And I don't think it's the solution. These issues are spawned deeper in the design. Multiple streams of information are being spawned, and must be handled sanely: pipe redirection starts breaking down here because it's a line - what's needed is a graph of management that's able to handle different cases and join back for the next approach.
One approach might simply be to develop a higher-powered programming language environment that calls directly into the system.
(My biggest complain about shell mode is that it's impossible to send certain characters to the underlying process, TAB being the most important one, so you can't rely on built-in tab completion behavior.)
I haven't worked much with it lately, but I wouldn't be surprised if Powershell was the closest existing technology to what the author is thinking of.
From the article:
Data structure. Windows PowerShell had a chance to
redesign the terminal from scratch, but defaulted to
the same old grid of ASCII. One innovative thing they did
do was add structure to their data, piping .NET objects
instead of raw text, allowing the user to select fields by
name instead of writing elaborate AWK scripts. The shell
for the research OS Famke does a similar thing for
higher-order functionsThere is also not much stopping you from using PHP, Python, Ruby, or anything else with a REPL as your daily shell, but bash is the most popular and works quite well for this problem domain.
Not to sound like an old dude stuck in his ways, but there is a reason that we're still all using VT 100 and 220 emulators from 30+ years ago -- they work great.
That's a fascinating idea. Know of anyone who does that?
No, they don't. Really. Look at the source code to ncurses and see if the millisecond timing loop around select() is still there, to distinguish between a terminal sending ESC[1D in response to you pressing "left cursor" and a human pressing "ESC" "[" "1" "D" very quickly :-)
It sucks. Windows got this right a long time ago, to the extent that the left & right modifier keys are distinguishable. Try doing that on a VT100.
Of course, a REAL VT100 doesn't have half the keys ; F1-F4 (IIRC) aren't sent "over the wire" and have no standard encoding. Linus basically invented one for the "linux" console terminal type, and lo yet another "standard" was born.
And don't talk to me about shells. The lunacy that is never quite knowing what insane metaquoting scheme you'll need today based on which arcane shell some moron has configured as the default for THIS particular machine is EXACTLY what the top-voted Koan is about.
This is relevant: http://stackoverflow.com/q/3637668/336455 In short, there are some objective reasons, not just popularity.
http://www.masteringemacs.org/articles/2011/10/19/executing-...
I want to be able to take the the best features from the command line, and the gui programs and package them up into something that just floats at the OS level. So that I use a keyboard shortcut to pull up a buffer that can grab text (or entire files) work on them and push the results back to whatever app/file I pulled it from.
Yup, via `!` and `r!`. See, for example, http://www.oualline.com/vim-cook.html#format_para.
I've always wondered about this; I sometimes get it (but don't know how to reproduce it) when trying to navigate. What does it mean?
I’m working on this in my spare time, starting with...
and now I'm curious to see what the author comes up with.
There's just something about an actual tool, no matter how prototypical, that improves the discussion of new tools.
You might type into a tiny window on one monitor that never loses focus, but sends graphs and text and streams to these windows.
There's no reason that the place you enter text should correspond to the output display, and a lot of value to be had by separating them.
Imagine being able to plug display consumers into a port so that you could do visual demos.
ETA at the last place I worked, we actually had the touchscreen on one desk and the program running in a window on another computer. It was pretty nice to type something and make it show up across the room.
Glad to read about the scenario at your last place - I've never seen this in action.
Of course, nowadays that's more commonly done with REST endpoints, which I think would satisfy your stdctrl idea.
I did some experiments with clojure/camel at one point, and came up with stuff like this:
(defroute context (from "file:/home/jw/scratch/inbox?noop=true") (to "file:/home/jw/scratch/outbox")) ; from http://codeabout.blogspot.com/2010/06/using-apache-camel-fro...
Which is basically a continuous file copy. I could see different flags for "do now and exit", "do at HH:MM:SS", "do until I tell you to stop", "do when system is idle", etc.
Could you perhaps explain a bit better?
I'd like for my terminal to be able to open a stream of html in my web browser. Use case: running `man blahblah` in a ssh session opens a nicely formatted page in a local browser window.
I'd like for my terminal to be able to open a stream of text in my editor, and accept a stream of text back from my editor to save somewhere. Use case: running `sudo -e /etc/blahblah` in a ssh session allows me to edit the remote file /etc/blahblah in a local text editor, and save my changes back.
Edit: or for a gui, something like Enso (for the whole OS) http://humanized.com/enso or Ubiquity https://wiki.mozilla.org/Labs/Ubiquity/Latest_Ubiquity_User_... (for the browser) Both are abandoned open-source projects with a lot of the hard work already done (the internationalized parser in Ubiquity is very nice).
Fun fact: Acme was Dennis Ritchie's editor of choice.
The two enhancements over the command line that I envision are the discoverability of commands and the ability to select the output of commands. So what you'd is an Enso/Vimperator like command interface where the output would be rendered as an 'object' or list of 'objects'. Each output object would be selectable and able to be used as input for other commands able to digest them.
You can sort of do this now with the command line but there are a few issues. The first is the inability to render graphical results in a terminal. The second is having to now something about the output of a command apriori before piping to the next command. Finally, it is difficult to know the commands available to your fingertips on the $PATH.
The more I meditate on a system like this the more I think it would be wildly productive because a wide host of problems can be solved with this single workflow.
COMMAND -> RENDER OBJECT(S) -> SELECT OBJECT(S) -> COMMAND -> ...
YMMV.
TermKit, for instance, is not just a widget-infested terminal. The core idea behind it is what >50% of this post is about: data interchange that's not un-tokenized text that you have to `awk` to hell and back to do basic things.
Meanwhile, text editors do two things incredibly differently than system-control interfaces: they edit blocks of text, and they can un-do almost every action. Next time you `rm` something accidentally, try pressing `u`, and see if it comes back. Or rewind that `drop database production;` your cat typed into your ssh session.
I also don't want Bash to be my editor for similar reasons why I don't want to manipulate my filesystem with Vim - I rarely need to enter visual select mode when composing something in Bash, and Vim is poorly-suited to piping streams of text through multiple programs.
I imagined links as something which when activated would be pasted in your command line. For example when running "git status" I would be able to get a ready made command to add a file by activating the "add" link next to it. Each file name would also be a link so that I don't have to copy/paste it. Ideally, links could be triggered with keyboard shortcuts to avoid using the mouse.
Links, as you describe them, can be implemented with javascript. I'll try to make an example on weekend.
I still think the idea is great. This guys should work together instead of making yet another competing project.
Both TermKit and this project will have an interesting dilemma with editing remote files though. The advantage of SSH is that you really aren't storing any remote files locally (only the currently visible characters are stored in memory). An editor that uses this new model and eliminates lag requires transfer of remote files to the local computer. There are a lot of situations where this is not a viable option.
This made Unix so reliable. If you want to write a beautiful terminal as _addon_ I have no problem with that. But I would not accept a _replacement_ of the old fashioned terminals. Because they are so simple, they just work.
The terminal guts are unbelievably gnarly, and it's kinda surprising it hasn't been replaced with a simpler approach designed for virtual terminals by now.
Because they ... just work? :-)
Here's the beginning of my thinking on the subject: http://blog.byjoemoon.com/post/9325300749/a-different-kind-o...
It's great to hear other voices in this discussion, though!
I've called it Semantic History. It also let's you drag files out of the terminal as well. Old video walkthrough: http://vimeo.com/21872771
It does not require any special ls. As long as there's a legit filename, it should work.
The hard part was my goal of getting it to work even if you change the working directory, so that paths that were legit before stay legit. I found out that my shell sends an escape code that updated the terminal title when it changed directories, so I hooked it into that, but it turns out that's oh-my-zsh specific.
I also added the ability for it to work even with spaces, which is essentially a brute-force, so it's not pretty.
In addition, the keyboard is often more effective than the mouse for our work, since instead of floundering around in nested menus we can just type what we want. However, it’s worth noting that we don’t avoid the mouse because it is slow — if one wants to move the cursor to an arbitrary location elsewhere on the screen, one can often do so faster with a mouse than a keyboard. The problem is the transition from the keyboard to the mouse. It’s an expensive context switch, which should not be done lightly.
I don't really understand the following:
We then add syntax highlighting and hyperlinks, so you can easily navigate between man pages, or click on a grep result to visit that line in a file. Clicking on a hyperlinked directory in a file listing would reveal the contents of that directory in a nested list, slightly indented; clicking on a file would open it in a new tab.
Too much clicking for my taste.
The core philosophy of Unix is to build tools that do one job well. By combining those tools, it is then possible to build great things. Do not assume that means you can hide the tools away and just give people the great thing, and realize it is naive to believe that you can solve everyone's problem by creating the one true master editor/program/os that combines all the great things from previous attempts, but this time "gets it right".
Certainly the provided successors of the Bourne shell might be more elegant. Certainly when piping data through several tools needs often transformation of the data representation to match the required input format. Sometimes the transformation uses different principles (regular expressions, shell wildcards, awk, sed, ..) which pollutes the logical flow of problem resolution. But I came to the conclusion that despite not being optimal, this data transformation noise holds information that, when reading or when needing to explain to others, helps to understand, or maybe remember the data model from the source to the sinks. However I believe, more uniform but more universal data transformation techniques would be a progress.
Until now this comment is more about shell than terminals, but for me, these are the biggest advantages of working on a command line - freedom and creativity in the usage of available tools.
Now, to come closer to the terminal aspect.
I am a typing fan. I went through hell when moving from Germany to France and having to re-learn a new keyboard layout - none of the both layouts are good, but if you are used to one it is very annoying to get to used to another. After having had some missions in other countries with different keyboard layouts, I found a solution, that is in line with my philosophy of using typing tools: Learn US keyboard layout, to the point to use it blindly without needing letters on the keys - it is installed on all OSes in all countries. At home use the extension US International with AltGr dead keys - I can now write all German, French, Turk and many other Latin based accents with a single layout. When in mission at a customer I ask if in the open session I can switch to US layout (if needed) - until now there were only some raised eyebrows, but no objections. And at least for ThinkPads you can order them with US layout, even with the € sign. So for keyboard I tackled the problem.
For text editors I resolved the problem already 10 years ago. I use VIM. VI is on all UNIXes, VIM is on Windows (I did not yet have to work on Macs).
On the UNIX shell the first thing I type is: set -o vi Like this many VI shortcuts and commands are at the command line.
One quote in the article made me smile the most:
"... However, it’s worth noting that we don’t avoid the mouse because it is slow — if one wants to move the cursor to an arbitrary location elsewhere on the screen, one can often do so faster with a mouse than a keyboard. The problem is the transition from the keyboard to the mouse. It’s an expensive context switch, which should not be done lightly. ..."
Yeah, this is the reason I use a track point instead of a mouse. Nothing to care with you, takes no space and you don't have to lift your hands from the keyboard. The only problem is the craving when having to sit at a customer at a keyboard that has not track point - I find myself sometimes searching for it with the fingers until I realize that I am not on my ThinkPad. It is a shame this device is disappearing on most computers.
At last: I think what unites the aficionados of the command line is the choice to spend more effort and time in learning tools which are more difficult than their alternatives (mouse vs. track point, command line vs. GUI, ten finger typing vs. two finger typing) at the beginning but pay big times off in efficiency in the long run and as a plus give the pleasure of creativity and freedom.
I encourage the author of the article to progress with his ideas! We absolutely need innovation in this space. It is just that the bar is huge because of all the tools we became used to.
VIM + touchpad beneath space bar on a standard laptop works well too. I can left\right click with my left thumb and move the cursor with my right thumb without my primary digits leaving the home keys.
(a) a good track point is ways more precise than a touch pad
(b) to cross the screen from one corner to another on a touch pad you have to make several strokes, whereas with a track point you don't have to leave the device a single time
GNU info?
Let's just replace escape codes with some kind of markup language (or s-expressions or whatever).
Huh? I didn't know the DEC could run software like Visual Studio, Explorer and TortoiseGit.
Whether you use an interface from the past or not is entirely a choice. Many developers apparently prefer it, and that's fine. I don't prefer it, so I use tools with a rather modern and well-designed interface, tailored towards developers.
If you really want to "reimagine" it, throw out the box and make a new one. If you redesigned all the standard unix tools to have a universal API and added hooks for each function they contain you could just specify a workflow to execute and the tools would figure out how to transmogrify the data internally. So for example:
rehooliginator --store=val1 --filesystem=/proc/cpuinfo --rowname='model name' --match='([[:digit:].]\+)GHz' --store=val2 --filesystem=/proc/meminfo --rowname='MemFree' --match='([[:digit:]]\+) kB' --store=val3 --cmd=ps --fields=rss,comm --sort=rss --match='java' --field=rss --sum --math='$SUM*1024' --store=val4 --cmd=vmstat --samples=5 --field=cpu-idle --avg --output="Stats:\n\tCPU: $val1\n\tFree Memory: $val2\n\tResident memory used by Java: $val3\n\tCPU idle time: $val4\n"
Not the greatest example but you get the idea. If this seems more complex than traditional one-liner scripting it's because you're trying to do a lot of little things on a single line. It may be better to shove all this into a little file in easy to understand non-programmer language and save it for later. (Also, the long GNU options could be replaced by short options for quicker use, depending on the API/module being used)This is obviously not getting away from the 'old school dynamic' of a fake terminal, but it does remove some of the need for it when we have tools robust enough that the terminal doesn't have to be as user-friendly as it is. You could combine a tool/framework like the above with a text editor to write multi-liners, sample the output and execute them on the fly. Build in hooks to execute commands over an ssh connection - or even gather output from various hosts at a time - and you could automate sampling your whole network from a one-liner.
For a "friendly interface" I think a simple tree view file browser would work nicely. So basically an "explorer"-type app with an embedded text editor and output window to let you explore a system rapidly and also automate tasks on the fly. Hell, you could build an IDE or other friendly GUI to build your query tool's arguments using quick mouse clicks.
Best Ivo
Not everybody uses their terminal to churn out HTML pages and add 'Nyan mode' to our 'newly discovered' emacs program. For those who do that, just buy a Macintosh or whatever is this week's hip flavor of Best Buy PC. Otherwise, use a language that doesn't require >256 different colors to be represented meaningfully.
"Typography is the future"? Thank goodness X.org/XFree86 has supported custom fonts since the 1990's.
"Opening a man page would scroll gently to the top of the page, letting you scroll down and read, or search through it as you would any text"
See: MANPAGER.
"We then add syntax highlighting and hyperlinks, so you can easily navigate between man pages"
Many terminals and shells support these features already.
"Finally we add visualisations so you can view plots of lines of code, etc., without having to context-switch."
Huh? I read that as 'code folding' and clang compilation.
I think the main takeaway here is that most of his "ideas" can be easily achieved within the current ecosystem of available programs, most of which are stock on modern UNIX-like OS distributions. I do think he misfiled this article under "Ideas"; it's more akin to a polite rant.
edit: colours/color killed due to conflict with reality (and irrelevance anyway).
Also, I'm British.
I don't dismiss the entire article; I appreciate thought and innovation in the space of the terminal, but I disagree with your ideas. Thanks for putting them out there to begin with.
I see the context-switch as one between text and graphics.
If I'm working on the command line, then most times I have no need to have X11 running. I'm working exclusively with text. I can boot to a command line and start working. No X11 is needed.
But when a need arises for graphics, e.g., to read a PDF composed of scanned images (not pure Postscript), then I have to "context-switch" to the X11 context.
I find that switching back and forth between these two contexts is not smooth and can easily lead to instability.
There is often a presumption, as in Plan9, that we will just switch once: to the graphical environment. And not return to the original console.
To me, neither an X11 terminal emulator nor the Plan9 environment is "the console". It's another layer of abstraction on top of the console.
That is a lot of overhead I do not need if I'm just working with text.
And even in the case I keep X11 running on another vt, I've found that when using no wm, or a simple one like evilwm, switching back and forth from console (on one vt) to X11 (on another vt) many times does not work well. Eventually it fails.
This is on {Net,Free,Open}BSD.
I don't think that Plan9 has vt's as such. It's more like what the article envisions, with graphics capabilities seemingly woven into the terminal. But you're pretty much stuck in an X11 type environment. Plan9 experts correct me if I'm wrong.
I've always found this "context switch" from console to graphics is like a one-way street. You're not really expected to keep shutting down the graphics and going back to the console. At least I've never found anyone who does that.
I'm a NetBSD user that uses a tiling window manager (i3 - not ion3, it's different). ALT+1 and ALT+2 are where I keep my urxvts, ALT+3 my web browser, etc. The switch happens instantaneously.
Am I mistaken in my understanding of your issue, or is this helpful?
Then the compiler will infer that you mean (4::Fractional a=>a) + (4.2::Fractional a => a)
However, you cannot add an integer and a float: (4::Int) + (4.2::Float)
Couldn't match expected type `Int' with actual type `Float'
In the second argument of `(+)', namely `(4.2 :: Float)'
In the expression: (4 :: Int) + (4.2 :: Float)
In an equation for `it': it = (4 :: Int) + (4.2 :: Float)
This follows from the type of (+) :: Num a => a -> a -> a(4.2::Fractional a=> a) + (4::Float)
Float is an instance of the type class Fractional. That is: methods which are defined for all fractional types must be defined for floats.
The compiler infers that (4.2::Fractional a=>a) must have type float, as it is being added to a float. This is compatible with the original type of the expression, as Float is an instance of fractional, so it is valid to read 4.2 as a Float.
This diagram might help: http://www.haskell.org/onlinereport/basic.html#sect6.3