comp.buetow.org

Two new books ordered

2010-03-07T18:46:48Z

The first book I've ordered is Programming in Prolog. This book covers everything I should know about Prolog for my next exam.

Originally published in 1981, this was the first textbook on programming in the Prolog language and is still the definitive introductory text on Prolog. Though many Prolog textbooks have been published since, this one has withstood the test of time because of its comprehensiveness, tutorial approach, and emphasis on general programming applications. Prolog has continued to attract a great deal of interest in the computer science community, and has turned out to be the basis for an important new generation of programming languages and systems for Artificial Intelligence. Since the previous edition of Programming in Prolog, the language has been standardised by the International Organization for Standardization (ISO) and this book has been updated accordingly. The authors have also introduced some new material, clarified some explanations, corrected a number of minor errors, and removed appendices about Prolog systems that are now obsolete.

This book was available for just 5 EUR (used)!

The second book I ordered is The Haskell Road to Logic, Maths and Programming:

The purpose of this book is to teach logic and mathematical reasoning in practice, and to connect logical reasoning with computer programming in Haskell. Haskell emerged in the last decade as a standard for lazy functional programming, a programming style where arguments are evaluated only when the value is actually needed. Haskell is a marvellous demonstration tool for logic and maths because its functional character allows implementations to remain very close to the concepts that get implemented, while the laziness permits smooth handling of infinite data structures.

I gonna start to read those books AFTER finishing my previous book which is still very interesting! :)

Structure and Interpretation of Computer Programs online Lectures

2010-03-06T11:09:53Z

I've mentioned this book once before.

Structure and Interpretation of Computer Programs has been MIT's introductory pre-professional computer science subject since 1981. It emphasizes the role of computer languages as vehicles for expressing knowledge and it presents basic principles of abstraction and modularity, together with essential techniques for designing and implementing computer languages. This course has had a worldwide impact on computer science curricula over the past two decades.

You can find the online videos and the free online book right here. For the case the ftp servers are busy you can download them from my own pub ftp instead (ftp.buetow.org/pub).

Terminal broken?

2010-03-05T21:16:17Z

A 'tput reset' should fix it.

Monads in C++

2010-02-28T21:38:22Z

Here is an example on how you could implement Monads in C++. Hrmm... I think I prefer the version of Haskell ;)

Here is a funny way of explaining Monads in Haskell (using Monsters devouring values).

nim Game in Haskell (Playing around w/ the IO Monad)

2010-02-23T22:45:35Z

http://cxg.de/_d0aef6.htm (Excercise of Lecture 9 of "Programming Haskell")

Working dress

2010-02-20T10:14:07Z

New book about functional programming ordered

2010-02-20T00:55:13Z

I've just ordered a new book (in german language) called "Funktionale Programmierung: Sprachdesign und Programmiertechnik " (in english "Functional programming: Language design and programming techniques"). This book is for people who know already a little bit about functional programming but want to dig deeper a little bit! It is demonstrating lots of stuff using functional programming languages such as Haskell and Opal.

VAX executable binaries on my x86!

2010-02-18T20:41:21Z

I was just looking around a little bit in the .git subdirectory of a local git repository of mine and found out that some files are VAX COFF executables!

pb@earth:~/DataTrap/git/science/.git$ file ./objects/e5/940c1148ae6050cdc20b5978fa7419b2b093eb
./objects/e5/940c1148ae6050cdc20b5978fa7419b2b093eb: VAX COFF executable

;)

VAX is a pretty old computer architecture which runs operating systems like OpenVMS:

Well, .. in real those are just binary blobs where git stores content in. A joke or by accident? Because OpenVMS' file system has integrated version control in its native file system. Its much simpler than git, but... ;)

Server reachable over 40 years ago

2010-02-14T11:47:15Z

I received the following notification from Hetzners monitoring robot just after shutting down one of the my VServers:

==> PING (reminder) <==  
State is now:   ERROR    (00:30h 2010.02.14)
State before:   UNKNOWN  (was over 40 years)

'Programming Haskell' online lectures

2010-02-14T10:51:47Z

I found a great series of free haskell lectures online at http://www.cs.nott.ac.uk/~gmh/book.html#videos. The referent is going through all the chapters of the book 'Programming Haskell'. The videos are pretty good and atm I am enjoying watching them. You should give them a try as well! I think you don't even need to buy the book in order to understand everything.

Update: I put those videos on my pub FTP server for download: ftp://ftp.buetow.org/pub/OnlineLectures/ProgrammingHaskell/

Nokia N95 8GB

2010-02-13T13:59:12Z

i bought myself a new cell phone. new is relative, but it is newer than my previous phone (se p910i) and the original n95 (which is owned by my girlfriend by now). since i liked the n95 i thought i should buy the n97 or at least the n96.

the n96 however is not the real successor of the n95. it is more the successor of the n85. i dont like the design of the n96. the fabrication of the n96 can not be compared with the fabrication of the n95.

and the n97 is a little bit too much. it is more than a small portable computer. it's not a cell phone anymore. at the moment the n97 is too expensive and not what i want.

but there is also a revision of the n95 available. it's the n95 8gb. it has more memory, a faster cpu, more storage, a bigger display, ... the n95 8gb isn't the newest cell phone available anymore, but fits perfectly my needs. I am able..

to phone and to write SMS messages
to read and write e-mail messages through IMAPS (using ProfiMail)
listening to local radio stations
downloading of podcasts and listening them offline
listening to mp3
online weather forecast
schedule of the local public transport, online and offline (java app)
alarm clock
browsing internet sites optimized for mobile devices (WLAN/UMTS)
taking pictures with the 5mp camera

here are a few pictures comparing the n95 (grey) with the n95 8gb (black):

And: Symbian, the phones operating system, has been declared as open source just a few days ago.

Redesign of the Fype Interpreter

2010-01-31T22:14:49Z

After reading Structure and Interpretation of Computer Programs I decided to rethink the interpreter of Fype. Fype is a small scripting language invented and implemented (in C) by me. I decided to take the code-base of Fype and to rewrite the core of its interpreter-part in order to use a Scheme/Lisp-like syntax. which is much easier to parse. The syntax is simpler and much more powerful now. So far it is now possible to define functions and sub-functions and to display all involving frames. Here is an example:

(def (test)
   (say "This is test")
   (def (test2) 
      (say "I am in test2" "And test3 will be defined next!")
      (def (test3)
         (say "Displaying all frames now:")
         (show-frames))
      (test3))
   (test2))
(test)

The invocation of the interpreter prints out the following result:

This is test
I am in test2
And test3 will be defined next!
Displaying all frames now:
FRAME(id=3) 0:
FRAME(id=2) 1:
+ST_LAMBDA(name=test3;args=)
( ( say Displaying all frames now: ) ( show-frames ) )
FRAME(id=1) 2:
+ST_LAMBDA(name=test2;args=)
( ( say I am in test2 And test3 will be defined next! ) ( def ( test3 ) ( say Displaying all frames now: ) ( show-frames ) ) ( test3 ) )
FRAME(id=0) 3:
+ST_LAMBDA(name=test;args=)
( ( say This is test ) ( def ( test2 ) ( say I am in test2 And test3 will be defined next! ) ( def ( test3 ) ( say Displaying all frames now: ) ( show-frames ) ) ( test3 ) ) ( test2 ) )

Now what's left to do: Implement a few more built in functions. And we have a new Scheme/Lisp-like language with a very very small footprint available :)

Btw.: This version of fype aims to be pure-functional and with lazy evaluation.

Book Tip: Structure and Interpretation of Computer Programs

2010-01-03T11:50:55Z

During Christmas break I read the book "Structure and Interpretation of Computer Programs - Second Edition" (by Harald Abelson and Garald Jay Sussman with Julie Sussman).

"The book should be read by every self-respecting computer scientist. Because of its clarity, simplicity, and wit, this work is highly recommended to anyone seeking an understanding of the emerging pradigms of computer science"

-- Mitchell Wand, American Scientist

This book handles all the topics using the dialect of Lisp called Scheme. It is impressive how simple a syntax and the interpreter and how powerfull the corresponding language can be. The book is mainly dealing with funcional programming techniques. I should overthink Fype, which is my own language for which I wrote an interpreter for.

Supporting Gentoo Virtual Servers (Xen DomU)

2010-01-02T09:07:49Z

Since a while I am offering Linux Virtual Servers (Xen DomU) and FreeBSD Jails at buetow.org. Until now I was only capable of offering Debian VServers and FreeBSD Jails. From now on I also support VServers running Gentoo.

Per User rc.d on FreeBSD using CSH

2009-12-30T14:40:43Z

On my FreeBSD Jail I've lots of users. And some of them require to start automatically an application in their homes at reboot (e.g. IRC bouncer or IRC bot). In order to accomplish this I wrote myself the following small script and placed it into /usr/local/etc/rc.d/zzz-usercs.sh (and set the executable flag):


#!/bin/csh
# (c) 2009 by Paul C. Buetow

set RC_DIR=rc.d

foreach user ( `cut -d : -f 1 /etc/passwd | grep -v '#'` )
  if ( -e ~$user/$RC_DIR ) then
    cd ~$user
    foreach rc ( ./$RC_DIR/*.sh )
      if ( -x $rc) then
        # Double Fork (Security reasons)
        (su -l $user ./"$rc" $1 >& "$rc.out" &) &
        chmod 660 "$rc.out"
        chown ${user}:wheel "$rc.out"
      endif
    end
  endif
end

Every user can now configure its own rc.d-scripts in ~/rc.d/. All scripts must end with .sh and they must be executable. The working directory is always ~ by default. The parameters are passed 1:1 to the individual user-rc.d scripts. E.g. ./zzz-usercs.d.sh start will pass start as its argument to all user scripts.