Tuesday, May 30, 2006


The other day, araujo suggested Erlang might make a good shell. Shell as in, bash. Hrm, I thought, maybe...
I don't think Erlang would be flexible enough to make a decent shell. Take something like this:

for i in *; do echo $i; done

What would the Erlang equivalent look like?

lists:map(fun(X) -> print([X]) end, ls())

I just don't see it? I should hope it doesn't look like that but I don't know. On the other hand, I seem to have it pretty set in my mind that Common Lisp would make an excellent shell language. A few people have told me that CL would probably be too verbose and not work out well but, I don't know, it just seems so succinct and powerful. You could make a lot of macros to make your life easier. I sent an email to the Lisp At Light Speed blog dude to get his opinion but I figured I'd post it here too to see if anyone has any thoughts.

What I have in mind is basically an interactive shell, using Common
Lisp as its programming language. For instance something like:

for i in *; do echo $i; done

Might look like:

(loop for i in (ls) do (print i))

The second thing I would love to see is Monad/Powershell. Rather
than using text to pass data around, uses lists/objects/etc. (ls)
for instance gives a list of file objects to iterate over, and you
can extract things like the size and permissions and what not.

This raises a question though. In order to do this, just about every
standard program becomes obsolete. For instance, why use 'cut' when
you can simply split a string with a CL function. However some
things would still be very useful, such as ls, or grep, but these
now need to communicate via objects rather than just text, so those
will have ot be rewritten. In which cause it seems like they could
simply be packages and loaded into the shell, meaning you don't
have to deal with program startup times or what not. Is this a lot
of work to rewrite all of these programs, and does it mean that we
cannot usefully use third party programs that people write? You
can always drop down to using strings as communication I suppose.

That is the basic idea. So far a few people have suggested that
sexprs really aren't any better for this sort of thing. sexpr's
won't be any better than say...bash. Someone suggested that Factor
might be a better language for this. But it seems to me, with
Common Lisps powerful macro system, you can easily make most
operations incredibly simple? The most useful aspect would be using
objects to communicate. But even if this is a lot of work to
accomplish, it seems to me that simply using CL as a shell programming
language seems like it would be nice. Am I wrong here? Am I missing

If CL would make a poor langauge, what would make a good language? Riastrach has suggested Factor. I don't know enough about factor to say that but I think I like CL better for this.

All I know is:

This is not the answer

Saturday, May 6, 2006

Pastebin design - Mnesia tables

I have started to design the tables for this. The main goal is simple: make it easily extendable. That is to say I want to make it so I can easily develope it incrementally and add things to it that I didn't think of before. But that should be obvious to any developer. Given the spec of my previous post, here is the beginning of the database.

paste - This is the table that will hold the actual pastes.
pid | text | annotation | language | date

pid - unique id to identify a paste
text - the actual text
annotation - any annotation the paster wants to include
language - Plaintext/C++/Erlang, etc
date - when they pasted it

highlight - cache of pastes that have been put through the source highlighter
pid | text | last_viewed

pid - the same as paste.pid
text - result of being put through the highlighter
last_viewed - to keep track of when the entry should be removed

threads - paste threads
tid | [pid]

tid - the unique id for a thread
[pid] - list of pid's

I decided to have the thread table just contain an id and list so you don't have to do a bunch of queries to get every paste in a thread. This way a paste can be part of multiple threads (Although I don't see when this will ever happen). The paste table contains, I think, the minimalist amount of data in order to be useful. Using a highlight table means we can store, if we want, every single paste with a highlighted copy of the text, or just a few and use it as a cache style system. Later on we can also add the ability to associate a paste with an irc channel or a user if we wish to track that sort of information.

I'm not sure how to generate unique id's in mnesia. In a SQL database I would use a serial data type but I am unsure if mnesia supports this functionality. If not I suppose I could use newref maybe? I need to be able to convert it to a string to make url's, and also be valid between restarts.

As I think about it, I guess serials are just implemented as a table and store the integer in there, I can implement that in mnesia I suppose. It just needs to have some sort of get_and_increment functionality so two proceses don't get the same idea. If anyone has any ideas on how to implement this let me know. Bear in mind I have not looked at the mnesia documentation yet and am just brainstorming, so it is quite possible the solution is incredibly simple.

Next step - determine what pages pages will be needed.

Thursday, May 4, 2006

Erlang Pastebin

I have always wanted to make a pastebin for some reason. When I first started looking at nevow, I wanted to make one in that however mg beat me to it (and made a kickass one at that). So now I have been looking at yaws and think it would be a good project. Perhaps it can be packaged along with the wiki and chat client. I think my pastebin is a bit ambitious, but I would like to design it in such a way that it can all be added incrementally so I can have a functional pastebin and add onto it.

For starters, I would like a nice clean layout. I am going to do my best to use CSS and valid HTML for all of this. I am hoping petekaz can possibly help out with this. I am going to write it with everything in a div tags with proper ids so it should be easy to give this thing a skin eventually.

Technical Features:
Syntax highlighting - As with any pastebin this will most likely be used for code 90% of the time. For all of those languages we need syntax highlighting so they are easy to read. I have found a program, I beleive it is just called 'highlight'. It handles 100+ languages, including all of the ones I have an interst in supporting so I can simply interface to that.

Documentation links - People seem to want this. I am not sure how easy it is to support, especially if you want to support a lot of languages. It's a thought but not on the top of my list.

Annotation - Instead of putting suplimentery information in comments of the paste, just having a section for such information would be nice.

Threads for pastes - lisppaste does this I beleive. A paste should be like a discussion. "Here this doesn't compile" "You have a mistake here, this fix will work" "Ok, but now I have a problem here" "Ok do this". Each post in a paste thread will have the paste + annotation. To reply, since you are generally going to simply be making small changes to the previous post, the paste section should be populated with that already.

Compile code for your language - I am not sure how to do this safely, if at all. It would be nice to provide a gcc interface and an erlc interface and a ghc, yadda yadda. But I am not going to put my system at risk just for this feature that shouldn't be needed all too much in the first place.

Interface to any erlang app - By providing a node + a process name, this should be able to send a message that paste is ready to any erlang node. The obvious first usage of this would be an IRC bot. The main problem I see with this is, depending on what application the data is sent to, that will affect the look of the pastebin. For example, if the events are sent to an IRC bot, you want to be able to select what channel the notification gets sent to for the IRC bot. Should I just hardcode this into the pastebin or provide some way for the IRC bot to register information with the pastebin and somehow have the pastebin display the information on the web app? This sounds a bit harder, but works better with any application (But what other applications would even want notification of a paste?). Perhaps I will hard code it at first and then move towards a more dynamic system as I figure out how.

Mnesia configuration - I like to use mnesia for my configuration. I have a config module which provides functions to be used in setting/getting values from the mnesia config data base. I also want to use mnesia to store all of the information for the actual pastes. I hear mnesia falls apart after store a lot of data, I can imagine some of these pastes will grow to be a fair size, so I am considering using a cache for the syntax highlighted pastes. Running the application to highlight the text on every hit sounds inefficient, and storing it for every paste sounds like a waste of space, so a cache is probably a good inbetween. Right now I would like to store as many pastes as I can but will consider deleting those that are too old.

Download paste - Being able to download the paste is always very helpful. Providing a nice filename that ends in the proper extension for the language would be nice.

Browsing recent pastes - You paste to my site you loste all privacy, go figure.

File upload - Somtimes it is easier to just upload a file rather than pasting.

This sounds like a lot but I don't think it will be too bad. It seems like I should be able to do most of it fairly modular.

Step one - Come up with mnesia tables, do some research on mnesia in terms of foreign keys and possibly how to do decent QLC queries. I think learning QLC will be important, especially when a lot of pastes get put into this thing.

Step two - Get the basic form for uploading going

Step three - Come up with step three when I get there.

Some obvious ideas were brought to my attention

Indent - Running various languages through astyle and friends would be very helpful, some people just can't indent properly.

Customize with cookies - Store various color information in cookies so people can keep colors they enjoy. This probably won't be implemented until much later.

Differences - Highlight differences between pastes so you can show what changes have been made. This sounds kind of difficult, especially if I am outsourcing the highlighting to a third party.

Line numbers - This should be obvious

Non GUI Browsers - Yes some people use these. The download as text option should be helpful for these people, but the probably also want line numbers so a specific Non GUI version of the code might be nice, this will include line numbers.

RSS - This certainly isn't a need but might be nice, especialy as the maintainer I might want to keept track of who's pasting what.

Intelligent Mouseovers - Showing balanced paren when the mouse is over