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Searching Haml files with ack

2012-05-14T00:00:00+02:00

This article describes how you can configure your ack settings to search for additionals files.

Recently I was working on a Rails project and was using Vim with the :Ack <pattern> command to search after a certain typed string “Übreschrift” and would like to replace it with the correct version “Überschrift”. I typed into the console :Ack Übreschrift and I couldn’t find a single match. What went wrong?

Questions to answer

Why couldn’t I find the file with that content? Was I in the wrong directory? No:

$pwd
-> $HOME/git-repositories/brokenlifts

Did I used the wrong pattern? No, I searched after the right word “Übreschrift”. Did I used the wrong command? No, I tried ack-grep in the terminal to search for other common words like test or string and could only find results in *.rb, *.js files but not in *.html.haml files. Tada, found the mistake, ack is per default not configured to include these very special file types.

Solve problems .ackrc

I created the $HOME/.ackrc and added the entries to include these special filename:

--type-add
html=.html.haml

Now my search worked and I got hits in *.html.haml files for searching after the term “Übreschrift”.

Since I’m working with Rails there are other file types like sass, erb, less, scss, .. I would like to include into the search:

--type-add
html=.html.erb,.html.haml,.haml
--type-add
css=.sass,.less,.scss

And there might be directories I don’t want to have in my search path. Let’s ignore them and speed up our search:

--type-set
ignorables=.log,.tmp,.pdf
--ignore-dir=vendor
--ignore-dir=log
--ignore-dir=tmp
--ignore-dir=doc
--ignore-dir=coverage

If you would like to see the specified files for your grep enviornment search, just use ack --help types - this will print all information you need. Here is an example:

$ ack --help types
=>
  --[no]actionscript .as .mxml
  --[no]ada          .ada .adb .ads
  --[no]asm          .asm .s
  --[no]batch        .bat .cmd
  --[no]binary       Binary files, as defined by Perl's -B op (default: off)
  --[no]cc           .c .h .xs
  --[no]cfmx         .cfc .cfm .cfml
  --[no]cpp          .cpp .cc .cxx .m .hpp .hh .h .hxx
  --[no]csharp       .cs
  --[no]css          .css .sass .less .scss
  --[no]elisp        .el
  --[no]erlang       .erl .hrl
  --[no]fortran      .f .f77 .f90 .f95 .f03 .for .ftn .fpp
  --[no]haskell      .hs .lhs
  --[no]hh           .h
  --[no]html         .htm .html .shtml .xhtml .html.erb .html.haml .haml
  --[no]ignorables   .log .tmp .pdf
  --[no]java         .java .properties
  --[no]js           .js
  --[no]jsp          .jsp .jspx .jhtm .jhtml
  --[no]lisp         .lisp .lsp
  --[no]lua          .lua
  --[no]make         Makefiles
  --[no]mason        .mas .mhtml .mpl .mtxt
  --[no]objc         .m .h
  --[no]objcpp       .mm .h
  --[no]ocaml        .ml .mli
  --[no]parrot       .pir .pasm .pmc .ops .pod .pg .tg
  --[no]perl         .pl .pm .pod .t
  --[no]php          .php .phpt .php3 .php4 .php5 .phtml
  --[no]plone        .pt .cpt .metadata .cpy .py
  --[no]python       .py
  --[no]rake         Rakefiles
  --[no]ruby         .rb .rhtml .rjs .rxml .erb .rake
  --[no]scala        .scala
  --[no]scheme       .scm .ss
  --[no]shell        .sh .bash .csh .tcsh .ksh .zsh
  --[no]skipped      Files, but not directories, normally skipped by ack (default: off)
  --[no]smalltalk    .st
  --[no]sql          .sql .ctl
  --[no]tcl          .tcl .itcl .itk
  --[no]tex          .tex .cls .sty
  --[no]text         Text files, as defined by Perl's -T op (default: off)
  --[no]tt           .tt .tt2 .ttml
  --[no]vb           .bas .cls .frm .ctl .vb .resx
  --[no]vim          .vim
  --[no]xml          .xml .dtd .xslt .ent
  --[no]yaml         .yaml .yml

Installing PostgreSQL gem under Ubuntu and Mac

2012-02-26T00:00:00+01:00

This article describes how to install the postgresql gem (called ‘pg’) under your local machine. The installation process is not trivial because you need to install the right packages: For Ubuntu/Linux you only need to install the right packages and for Mac you need to specify the correct path.

I checked out a new rails app called Broken lifts. Broken lifts in public transportation are annoying and limit the mobility of people in wheelchairs. The app provides status information from different operators on one page and shows how well they are performing.

Ones I checked out the project I have detected that it uses PostgreSQL as their database driver. So far I have never worked with it and I run into a couple of problems to get it running.

The problem

A small $gem install pg brought me the following error message:

$ gem install pg
Building native extensions.  This could take a while...
/Users/helex/.rbenv/versions/1.9.2-p290/lib/ruby/site_ruby/1.9.1/rubygems/ext/builder.rb:48: warning: Insecure world writable dir /Users/helex/bin in PATH, mode 040777
ERROR:  Error installing pg:
	ERROR: Failed to build gem native extension.

        /Users/helex/.rbenv/versions/1.9.2-p290/bin/ruby extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
\*\*\* extconf.rb failed \*\*\*
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/Users/helex/.rbenv/versions/1.9.2-p290/bin/ruby
	--with-pg
	--without-pg
	--with-pg-dir
	--without-pg-dir
	--with-pg-include
	--without-pg-include=${pg-dir}/include
	--with-pg-lib
	--without-pg-lib=${pg-dir}/lib
	--with-pg-config
	--without-pg-config
	--with-pg_config
	--without-pg_config


Gem files will remain installed in /Users/helex/.rbenv/versions/1.9.2-p290/lib/ruby/gems/1.9.1/gems/pg-0.13.2 for inspection.
Results logged to /Users/helex/.rbenv/versions/1.9.2-p290/lib/ruby/gems/1.9.1/gems/pg-0.13.2/ext/gem_make.out

What relevant about the mess up there is the following part:

checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no

Ruby can’t find the relevant setting of the PostgreSQL installation. Let’s change this!

Solution for Mac

install PostresSQL library as described on the PostgreSQL page (opening the *.dmg file will install a bunch of stuff, so don’t be afraid of the amount of steps you have to perform)
check if you can find the installation open it under /Library/PostgreSQL/x.y - where x.y stands for the version you installed

Say you want to install the PostgreSQL manually with a gem install - you have to perform the following command

$ sudo PATH=$PATH:/Library/PostgreSQL/9.1/bin gem install pg

If you want to install it with Bundler, run the following command

$ sudo PATH=$PATH:/Library/PostgreSQL/9.1/bin bundle install

Please change the 9.1 with the version you have installed. Thats it!

Solution for Ubuntu/Linux

It is easier because you only have to install the right packages:

sudo apt-get install postgresql
sudo apt-get install libpq-dev

Now gem install pg should work.

Conclusion

It can be a really pain if you want to install gems and don’t have the right dependencies on your machine but if you initially invest some time on the problem, you have your enlightenment.

Compiling Vim from source for Ubuntu and Mac with ruby and python support

2012-02-19T00:00:00+01:00

This article describes how to build Vim (vim and gvim) from the source and compile it against a predefined version of ruby installed with rbenv. In the first chapter I describe how to build it from source for Ubuntu. The second part describes how to build for MacVim.

By installing Vim with ruby support from the sources, it is build against the system wide installation of ruby. If you already installed Vim and/or ruby with sudo apt-get install vim (or sudo apt-get install ruby) or with brew install vim (e.g. brew install ruby) if you are using OS X, remove it completely from your system to install the latest version of Vim.

Install rbenv

I’m installing rbenv on different machines so I created the following script (named rbenv_install.sh) to install ruby 1.9.2-p320:

cd $HOME
sudo rm -rf .rbenv
git clone git://github.com/sstephenson/rbenv.git .rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile

# install steps for rbenv-install command
cd $HOME/Downloads
sudo rm -rf ruby-build
git clone git://github.com/sstephenson/ruby-build.git
cd ruby-build
sudo bash install.sh

# updating the current shell
cd $HOME
exec $SHELL
source $HOME/.bash_profile

rbenv-install 1.9.2-p290
rbenv rehash
exec $SHELL

After this try the following:

$ rbenv global 1.9.2-p320
$ rbenv local 1.9.2-p320
$ ruby -v
=> ruby 1.9.2p320 (2012-04-20 revision 35421) [i686-linux]

The crowd applauds.

Get the latest version of Python

This will be put in the $HOME/lib folder

$ cd $HOME/Downloads
$ wget http://www.python.org/ftp/python/2.7.2/Python-2.7.2.tar.bz2
$ tar xjvf Python-2.7.2.tar.bz2
$ cd Python-2.7.2
$ ./configure --prefix=$HOME
$ make && make install
$ make inclinstall # install headers, otherwise Vim won't have Python support
$ hash -r

Get the latest version of Vim

Visit vim.org and select the right download for your operation system (mainly Unix). If you are using a Unix system yo can get the lates vim from here, download and unzip it:

$ cd $HOME/Downloads
$ wget ftp://ftp.vim.org/pub/vim/unix/vim-7.3.tar.bz2
$ tar -xjvf vim-7.3.tar.bz2

You can also get the lastest Vim version from the git repository with the following command:

$ cd $HOME
$ git clone https://github.com/b4winckler/vim
$ cd vim.git
$ git tag -l
$ git co v7-3-515

Compiling Vim and gvim

To install gvim on Ubuntu we need to install additional packages on our machine. The followoing snippets describe the packages for Ubuntu:

$ sudo apt-get install libncurses-dev libgnome2-dev \
 libgtk2.0-dev libatk1.0-dev libbonoboui2-dev libcairo2-dev \
 libx11-dev libxpm-dev libxt-dev

Since we are now having the vim sources under $HOME/Downloads/vim73 it’s time to start the compilation. First we need to configure our compilation:

$ cd ~/Downloads/vim73
$ ./configure --prefix=/usr/local \
    --enable-gui=no \
    --without-x \
    --disable-nls \
    --with-tlib=ncurses \
    --enable-multibyte \
    --enable-rubyinterp \
    --enable-pythoninterp \
    --with-python-config-dir=$HOME/lib/python2.7/config/ \
    --with-features=huge \
    --enable-gui=gnome2

Let’s get over the heavy stuff:

--prefix=/usr/local - place of the binaries of the installed Vim installation (check the /usr/local/bin) - there will be the executable binaries
--enable-rubyinterp - says you want to build Vim with the default ruby installation (in our case /home/mg/.rbenv/shims/ruby)
--enable-gui=gnome2 - building Vim with GVim support (if you don’t want GVim than you can leave this line out)

After configuring the compilation check if the console response contains the following terms:

checking --with-ruby-command argument... defaulting to ruby
checking for ruby... (cached) /home/mg/.rbenv/shims/ruby
checking Ruby version... OK
checking Ruby header files... /home/mg/.rbenv/versions/1.9.2-p320/include/ruby-1.9.1

If you can’t see the lovely Ok, your vim compilation will probably not have ruby support. After that we can build the configuration, install, and clean everything up:

$ cd ~/Downloads/vim73
$ make
$ sudo make install
$ sudo make clean

Check the installation

Open a new session or perform exec $SHELL to reboot your Shell. You will see the fresh installed version of Vim:

$ which vim
/usr/local/bin/vim

$ which gvim
/usr/local/bin/gvim

Next check is to get the correct –version of vim and gvim with the following commands:

$ vim --version | ack ruby
$ vim --version | ack python
$ gvim --version | ack ruby
$ gvim --version | ack python

If both commands return +ruby and +python, you are fine, and got the achievement “I installed vim form source with ruby support on my own”. You should now be able to run the Hammer.vim plugin - install it, start it with :Hammer, install the missing gems and if you are able to run :Hammer without any missing dependencies, you have setup everything correct.

Installing MacVim from source

The ways are nearly the same as mentioned above: Install rbenv as mentioned in the steps before.

$ cd $HOME/Download
$ git clone git://github.com/b4winckler/macvim.git

Next step is to configure MacVim for OSX:

$ cd macvim/src
$ ./configure --prefix=/usr/local \
              --with-features=huge \
              --enable-rubyinterp \
              --enable-pythoninterp \
              --enable-perlinterp \
              --enable-cscope

After configuring the compilation check the console response after the following terms:

checking --with-ruby-command argument... defaulting to ruby
checking for ruby... /Users/helex/.rbenv/shims/ruby
checking Ruby version... OK
checking Ruby header files... /Users/helex/.rbenv/versions/1.9.2-p320/include/ruby-1.9.1

When this is finished, it is time build MacVim with make:

$ make

Next step is to run the MacVim installation:

open MacVim/build/Release/MacVim.app

The window should open MacVim. Run the following command in the MacVim quickfix window:

:ruby puts "MacVim"

In the next step, you can drop the MacVim.app icon in your Application folder and you are done.

Conclusion

It was a pain to gather the information for building vim by source with rbenv. Duration of finding that was: ~ 6 h. I’m not sure if all of this works on RVM - I just need additional feedback from people using it. Happy “Vim-ing”!

SMART principle

2012-01-12T00:00:00+01:00

This post is about the SMART principle that helps you to start and keep rolling projects. I outlined how I use SMART for my eBook project.

I recently read the book Pragmatic Programmer, in which Dave Thomas explained the SMART principle. SMART is an acronym and each character of the principle has the following meaning:

S (specific goal) - what is the goal of the new project you want to start
M (measurable) - list all the features you need to accomplish to start the project
A (action) - when will you start
R (realistic) - is the project small enough to finish it in the specified time frame demanded time frame
T (time) - in the beginning of July 2012 everything should be fine

Putting theory into practice

Late in 2011, I started a new and personally ambitious project: Writing an eBook about the great web framework Padrino. In a first step, I created a rough road map, about what I wanted to write and which topics should be covered. After writing the intro section and pushing the resources to github I did something very crazy and mentioned @padrinorb in one of my tweets and this was it – the authors of the framework motivated me with with writing the book. They retweeted every small progress I made with the project and through that I got further pull requests and even a bunch of interested followers who are watching the project.

Let’s see how I can formulate the Book project with SMART:

S (specific goal) - I want to learn how to write a eBook easily about Padrino web framework
M (measurable)
- create roadmap about the topics of the book
- find a method to write book in one format and export the as pdf, epub, mobi, and HTML format
- get really involved in Open source community and communicate with them
- find an audience and get help from other people
A (action)
- start as soon as possible
- try to write everyday one chapter of the book
- tweet about the progress I made everyday
R (realistic)
- it is a big project (never have written a book before) but continuously delivery will motivate me during this long period
T (time)
- till February 2012 everything should be finished

I set up the frame of SMART goals and developed a rough plan - that’s all you need to let come your dreams true.

Cost for SMART

To be honest, writing of my Padrino eBook project consumes a lot of my free time so I in the near future I will publish only a few new entries on this blog. I have many ideas and topics I want to cover, but first I will finish this book to deepen my writing experience. I’m glad to hear your opinion (or contribution) to the book - I will put every contributer on the special thanks list of the book.

Conclusion

SMART is great if you want to start in small steps to begin with something completely new, learn much about it, and report (for example, I’m using the twitter hashtag #dailywriting) about the progress you made.

Thanks to Sebastian Guenther for reading an earlier draft of this post.

Global Coderetreat 2011 in Berlin

2011-12-04T00:00:00+01:00

I attended the Global Coderetreat¹ event initialized by Corey Haines². The general purpose of this event was to get a bunch of hackers together to implement Conway’s Game of Life.

Setting up goals

As J. B. Rainsberger mentioned in his article article four elements of simple design, it is best to setup goals for your retreat to get most out of it. Here is a list of what I achieved in each session:

Being a mentor of TDD: I taught dedan how to use TDD, why TDD helps you to think about your design
Being a mentor of BDD: Showing a fellow Rubyist how to do BDD
Doing something completely stupid: I played evil coder and ping-pong pairing with @tilosoenke - we couldn’t communicate with words, only with code, one writing tests and other the implementation of the tests.
Discuss about names: We said together and discussed about right names for methods, variables, and classes. We concluded that good names saves you scary comments in your code
Explain Ruby to a Java-Programmer
Being mentored about Lisp: We solved the whole ‘Game of Live’ in common Lisp³, while @HansHuebener explained me the strength and beauty Common Lisp.

Conclusion

It was great to get so many people with so many different skills and mindsets together, exchange experience and encouraging others to try something new. I will definitely have a closer look on Lisp to enhance my Ruby programming style.

Thanks to Sebastian Guenther for reading an earlier draft of this post.

Benefits of Scala

2011-10-29T00:00:00+02:00

When a new programming language is created, it came from a desire of one person or a group of to do it better than their forerunner. It’s an evolutionary process that humans are trying to improve themselves if something doesn’t as they want it to. Sometimes it’s only a small piece of improvement which creates an absolutely new feeling about something. By designing a new programming language you have a great pool of existing languages: LISP (1958), Smalltalk (1970), C++ (1979), Python (1991) and Ruby (1995). Today it is often told not to waste your time on building up an new language from the scratch. It’s time-consuming and why should you invent the wheel a second time? I think this is just normal. If you spend some time reading about the languages mentioned above, you will see that older language have still a great influence on new ones. Today, it is common to use DSLs (they are used extensively in Rails) to create new languages. Not everything happened in the past was bad and sometimes if you stick your head into some old forgotten technology you may find some diamonds.

This was the main idea of Odersky when he created Scala. It is the first language which is a real hybrid language and combines the invigorations of OOP and FP.

Main facts about Scala

Scala is ideal for today’s scalable, distributed, component-based applications that support concurrency and distribution.
Scala is statically typed that means that the type of some variable is immutable during the whole execution of the program.
There is modular mixin-composition for classes - some hack to enable multiple inheritance in Scala, which solves the diamond problem through linearity of the inheritance hierarchy via traits.
Liquid error: undefined method `join’ for #
Lower risk to use Scala in an existing Java Application because Scala works seamless with existing Java Code.
high level type system with variance annotations, compound types, lower and upper bounds for types
usage of inner and anonymous classes
implicit conversions - that means a function take one type as an argument and returns to another type (like converting an Integer into String)

Conclusion

Scala is a very rich language which combines many features of different languages. It’s great if you have to make different sections of your code cleaner, faster and conciser. See Scala at Linkedin to know what I mean.

Thanks to Hanna Schuett and Sebastian Gerth for reading an earlier draft of this post.

Mail Client in Java

2011-10-22T00:00:00+02:00

During the summer term 2007 we had the task to create a Thunderbird¹ like mail client in Java².

The GUI should be created either with Swing³ or AWT⁴. Beside the graphical implementation, we had to check and study the functionality of POP3⁵ and SMTP⁶. Only the correct numbers in this protocols are important because they stands for each transactions if it was a success or a failure. A first attempt this functionality was done with plain old sockets to get a feeling how POP3 and SMTP works.

After we a running function the basic functions of the mail client, we had to implement some extra-functions like attachments (mime parts in an email) or the handling of emails with drag-and-drop. I implemented this big project with the help of NetBeans⁷.

Images

By means of the following images I will describe the basic layout of my mailclient.

The basic surface when the program starts. If you press on the upper task bar a drag-and-drop menu will open.

In this window you can add data of a new account.

Get the mail of an already existing account.

The window where to write a new email.

Drag-and-Drop window to manage emails.

Installation for Netbeans

get the sources from github
extract the javamail-1.4.zip => this package contains a Java library for handling emails
create a new project under NetBeans and copy all files of the Mail Client directory in the src directory of you NetBeans project
then you have to insert the mail.jar file in your project in the following way:
- click right on Libraries in the near of the view of your NetBeans project and chose Add JAR
- navigate to javamail-1.4 folder and select the mail.jar
- when you now select the files GUIMailsend.java and GUIMailsget.java should not show any errors
now you have to adopt the paths in the file GUIMain.java (static File f, String dir, FileReader file) and GUITree (File driveC, File source, File ziel) to your NetBeans project folder through absolute paths => I know it’s cumbersome but due to this date I couldn’t do any other
set the GuiMain.java as the main file in your project and start the program
the standard account is MG kontoinfos.kondat which contains the necessary data to access my spam account (you can guess how to change the data)
the directory Inbox MG saves all read mails of the user MG, further accounts have to be created each in an own directory
MailApi.java is not necessary for the mail client, this will just be used to check the correctness of the POP3 settings via the terminal
main cause of error messages:
- wrong paths to your project
- POP3 and SMTP
- mail.jar is not included correct in the project, but this will be shown in NetBeans

Conclusion

This project was my first big piece of software and I used all my gathered knowledge about Java. The classes are not bug-free, manually tested, has a size over 1000 locs, has absolute paths, and the function are sometimes very big. In the end it was just hacking down the software without using certain patterns or careful development with clean code. I tested my code with System.out.println and I lost so much time with this stupid testing. One good thing I did: I created comments and was able to get the program running even after two year.

Nowadays programming methodologies like Agile⁸, Rapid-Prototyping or Model-Driven development together with the framework Rails let you develop my application with much more less effort and is more maintainable by driving the Test-Driven way, so you can refactor your code and don’t need to manual test part of your basis.

This project shows that it is possible to develop modular software in Java but in even greater projects it is easy to get lost in the lost in Java code if you don’t rely on a framework. It is even difficult to setup the project in different IDE - today you can use Vagrant⁹ to create an environment which can be deployed easily as Virtual images on different platforms.

Benefits of reading a book - and use it right after that

2011-10-15T00:00:00+02:00

It’s a typical situation which every person knows: You look on your workspace and have a bunch of new books there. You ordered them because some great guys lay their hands in the fire that you need this wisdom. Of course you have to do a stressful job and don’t have time to read all the things but you still must learn new things in order to develop new skills. What should you do? I just started reading as much as I can.

What you should do during the process of reading

Don’t just read the book and put it away, read trough the table of contents, mark the parts which are interesting for you and draw a mind map. If you have questions which should be answered by the book, it’s good because then you will read the book with much more focus on them.

Don’t just think of reading the book like in school: Cram for a test about it, get a good grade and then just forget everything. This isn’t good and a waste of time. Don’t say you don’t have time, just think of allocating your time effective. For me it’s the best, just to use the new knowledge out of the book. This is the best way to get the most out of it. What you’re right using is just as good as cooking a new meal right after reading the recipe of it. You just inherit the procedure you recently learned with your own mind, own feelings, own observations and add your own style (think of your own ingredients in your favorite meal).

Benefits of note taking

Years after reading the book you will maybe come in the situation where you need some of the knowledge you just have read of this certain book you read it a lot of years ago. You know the title of the book but can’t remember anything. Before I explain the advantage of taking notes during reading a book, I suggest you my different methods for taking notes:

a pencil and a sheet of paper (which I personal prefer)
netbook/iPad/handy (there you can directly take your notes)
you can use post-it or stick it to mark important passages
speaking notes of certain passages which you find very interesting
read an eBook with your kindle, iPhone or some other devices in which you can take custom-notes about something

The disadvantages of 1, 2 and 3 are carry the notes respectively the book with you (think you are on your trip to America and don’t want to fill your hole luggage with tons of books or do you want to travel without your favorite Simpsons trousers).

Method 4 is just a reminder of important passages. If such a file is very long you have problems in searching the needed sections - you have to play forward and back and this is boring. Don’t forget the amount of space which you need to store it. The advantage is, that you can easily take notes and train your language when your tongue is on air.

The usage of a specialized device for eBook-reading is a great opportunity. You can have many books on on your device, set bookmarks and can take notes. I think writing notes without a keyboard may have a worse usability - maybe with the iPad 2 its more easier. Of course, if you are used to this technology and you are are good then just use it. You can make it public or lock it with a certain password. But why hidden your knowledge so that no other one can see it? Let other benefit by your conclusions and wisdom.

Personally for me the best method is to write my impressions of a read book on a sheet of paper and transform with my PC later. A further step may be publishing your notes to your website - so you have the possibility to access your thoughts just via an Internet connection. I’m using a desktop-wiki zim and wrote a bunch of handy scripts, which transform the text directly in format of my web page.

Conclusion

If I had known early I would have started with this methods during my education at school. But better later then never. If I travel for a longer period and have a book with me, it has still some sheets of papers in it, so that I have space to take notes. A pencil is for me standard equipment. So I can put every place where I read a book my thought about it on paper. If the book is finished and I have a little bit time left, I will transform it into my netbook and then have my thoughts with me.

So remember: In the beginning it’s just unusual to make several breaks during reading a book, which breaks your normal flow of reading. But during these breaks you can reorder your thoughts about certain things and get new insights. I suggest to publish it online and then see what will happen with it.

Thanks to Hanna Schuett and Sebastian Gerth for reading an earlier draft of this post.

Why learning a new programming language

2011-10-08T00:00:00+02:00

“Why should you start learning a new programming language” was the questions I asked me in the 2011? Nowadays we are all to busy to try new things, to expand our horizon. After reading the Pragmatic solving problems In the following chapter I will explain you, how I learned programming languages.

In the beginning there was Turbo Pascal

The first language I learned was Turbo Pascal. Everything (not only the programs) looked like a great “geek nerving god tool”. I quite don’t understand what I was doing with Turbo Pascal as my computer science teacher told me to make some simple calculation the perimeter for triangular and other geometric object. It was great to declare your variables and then put them into a function and print line the outcome. Here are some images:

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Turbo Pascal was my first procedural language and later during my studies I learned in a lecture about compiler construction that this language was developed 1970 by Niklaus Wirth (whom I admire for building such easy and effective techniques like the recursive descendant, but thats another tale). If you want to have this retro feeling just check out Ubuntu resources (or other things if you want to stay up).

The following images show the “IDE”. It has few options with fancy looking buttons and no options-overload.

In secondary school we had written some programs in Delphi (original it had the name Object Pascal). The new things was that even the girls had little fun in writing programs in it (some nice “Hello Kitty” in with pink color, but they actually love it). We learned how to write functions and to create some appealing graphics. After that I lost my interests in programming because the age of warhammer or video games.

Then Java came …

When I started my studies of computer science I knew I had still no programming experience and during my first year I had to learn Java. It was quite good and quite bad if you ask my. The good things about it was that I had to learn an exhausting new methodologies: OOP, Interfaces, Recursion, Inheritance, Encapsulation, Polymorphism and many other concept. I was lost, I just wanted to learn how to write simple programs and no one could tell me, why I have to write this public static void main (String args[]) to start my program. My fellow students told my that I was an absolute newbie (they were actually right).

Chad Fowler wrote in his book The Passionate Programmer: “Always be the worst guy in every band you’re in.” I actually was it and in now time I made great progresses. But some aspects of Java hit my but: It was so long to express simple things, so much overhead with static, private and so on. To what I mean have a look on the following code:

class Socke {

  public String farbe;
  public int gewicht;
  private boolean istTrocken;

  void trockne() {
    istTrocken = true;
  }

  void wasche() {
    istTrocken = false;
  }

  boolean istTrocken() {
    return istTrocken;
  }
}

public class NewClass {

  public static void main(String args[]) {
    Socke stinki = new Socke();
    stinki.farbe = "schwarz";
    stinki.gewicht = 565;
    stinki.trockne();
    System.out.println(stinki.istTrocken());
  }
}

Ok, you may say: “It’s quite readably” but wait until you have written, about several kilo of locs and want to maintain or refactor it. I thought that I could understand my “well” written mail client but well afterwards you know it better.

For another term I looked on C++. It was good to see how pointer (or references) are working, how you must allocate your memory (Java has it’s gc) and generics (or templates) for your data structures. I nearly learned something new, C++ is like Java, it’s OOP and you can program procedural if you like to. Have a look on some code:

/*
* 2.1
* Author: Matthias Guenther
* function: repeated shortening of breaches with a ggT
* use the Euklid-Algo to compute the ggT
*/

#include <iostream>
using namespace std;

int compute_ggT(int a, int b){
  if (b == 0){
    return a;
  } else {
    return compute_ggT(b, a % b);
  }
}

void shortening_breach(){
  int a, b, shortening_factor;
  string q;
  do {
    cout << "Please input the parameters to solve the breach: a/b\n";
    cout << "[Input] Parameter a: ";
    cin >> a;
    cout << "[Input] Parameter b: ";
    cin >> b;
    // look at the ggT
    if (b == 0){
      cout << "This is not allowed";
    } else {
      shortening_factor = compute_ggT(a,b);
      a = a / shortening_factor;
      b = b / shortening_factor;
      cout << "The breach is:" << a << "/" << b << "\n Continue?"
            "\n [Input \"q\" to leave the programm or \"c\" to "
            "continue]";
      cin >> q ;
      cout << "\n ";
      }
    } while (q != "q");
}

int main(){
  shortening_breach();
  return 0;
}

Enlightenment with Ruby

Normally I’m not the guy how runs after every hype but I haven’t found so far my beloved programming language. Why not risk a look. And then there was this ‘Whosh’ (think DC Comics). You could program in different styles, could design your own languages (called DSL) and this nifty framework Ruby on Rails (RoR) with Test-Driven Development (TDD), Behavior Driven Development (BDD), Continuous Integration (CI) and many more things. These things sound a like a mystery for me, but just get started and see how “easy” you can use it with RoR. It hits my head.

It was a very hard steady learning curve but it was more pleasantly then just go to the candy shop and get what you want for nothing. You have to invest much time. But look for yourself on ruby - it looks like a natural language. Just look at a script I wrote to tag MP3:

require "mp3info"

# setting the basedirectory
base_directory = "check/"

# run through all directories and get the mp3
Dir["#{base_directory}**/*.mp3"].each do |mp3|
  # get the directory
  arr_directory = mp3.split("/")[0..mp3.split("/").length-2]

  # empty string which will be merged to a string and which is needed for file renaming as a path
  directory_of_album = ""
  arr_directory.each do |part|
    directory_of_album << part + "/"
  end

  directory_of_album = directory_of_album.gsub("//", "/")
  mp3_track = ""

  # open the mp3 to read the id3 infos
  Mp3Info.open(mp3) do |track|
    # delete genre
    track.tag2.TCON = "Game"

    # check, if the track title exists
    if track.tag.title != nil
      # mp3 with an underscore are translated in / so we must catch this
      track_string = track.tag.title.gsub("/", "")
      track.tag.title = track_string
    else
      puts "Please set the track-tag for #{mp3.split("/").last} ... NOT converted"
    end
    # save mp3 tag
    mp3_track = track
  end

  # rename files
  if mp3_track.tag.title != nil
    mp3_newname = "#{Dir.pwd}/#{directory_of_album}#{mp3_track.tag.tracknum} - #{mp3_track.tag.title}.mp3"
    output = mp3_newname.split("/")
    File.rename(mp3, mp3_newname)
    puts "#{output[-1]} ... converted [#{mp3_track.tag.album}]"
  end
end

Automating tasks

I resisted very long to learn the bash, but there were so many tasks over the years which I didn’t do because t gives me the heebie-jeebies to do the same thing over and over again. After one weekend studying the open book “The Linux Command Line” by William E. Shotts I caught fire. For a long time I messed my desktop up with tons of images with ugly names, so I wrote a script to change this.

I have a bunch of images with ugly name, so I wrote a script to change this. Each command has it’s purpose you have to learn its syntax. Here is some sample code (pretty neat):

#!/bin/bash
z=`ls | wc -l`
z=0

for i in *.jpg; do z=$[$z+1]; mv "$i" ${i##*.jpg}$z\_$1.jpg; echo $i ; done # replace watermark_ (prefix)

It’s like Lego, you have these and that, plug it together to create something new. For my diplom thesis I create a Rakefile (the modern version of make written completely in ruby):

desc "Create a directory for the compiled classes"
task :create_class_directory do
  system 'mkdir -p classes' # overwrite the directory if it exist
end

desc "compile the plugin and put the files in the directory"
task :compile_plugin do
  system 'fsc -d classes Plugin.scala'
end

desc "copy the plugin descriptor"
task :copy_plugin_descriptor do
  system 'cp scalac-plugin.xml classes'
end

desc "create the jar file"
task :create_jar_file do
  system 'cd classes; jar cf ../divbyzero.jar .'
end

desc "create environment"
task :create_environment => [:create_class_directory, :compile_plugin, :copy_plugin_descriptor, :create_jar_file] do
  puts 'done with creating the jar file ...'
end

desc "compile the traits"
task :compile_traits do
  system 'fsc -d classes TraitProgrammingHelper.scala'
  system 'fsc -d classes TraitUpdaterHelper.scala'
  system 'fsc -d classes TraitArithmeticRulesHelper.scala'
  system 'fsc -d classes TraitBasicRulesHelper.scala'
end

desc "create environment with traits"
task :create_environment_complete => [:compile_traits, :create_environment]

desc "run example file"
task :test => [:create_environment_complete] do
  system 'scalac -Xplugin:divbyzero.jar Example.scala'
end

# ...

Head scratching with Scala

I learned this language for my diploma-thesis, otherwise I still wouldn’t put a thumb on FP. So far I must say that it was a good decision to learn an functional language. Scala showed me how to use chained function, anonymous functions, currying, type bounds and many more constructs. In the beginning my head howls like a steam-tank, there was so much new terrain for me that I need several breaks to get used to it. After many hours of happy cramming I got surprisingly insights in doing OOP better. That was is, what the Pragmatic Programmers were preaching. To get new insight in a technology you have to regard it’s counterpart. Don’t hesitate to do something you would never do, you gain experience and more confidence in your profession.

Here is some of Scala code:

class Reference[T] {
  private var contents: T = _
  def set(value: T) { contents = value }
  def get: T = contents
}

object IntegerReference {
  def main(args: Array[String]) {
    val cell = new Reference[Int]
    cell.set(13)
    println("Reference contains the half of " + (cell.get * 2))
  }
}

Conclusion

This was my first essay. I tried to cover the things which whom I’m actually dealing. I presented my wide route from my programming experience so that you can see, how the things evolved for me. I always get my hands dirty and try to roll up my sleeves to get a touch about the newest technology. I think through adventuring you become each day a little bit better then yesterday.

Thanks to Hanna Schuett for reading an earlier draft of this post.

Method alias in ruby

2011-10-01T00:00:00+02:00

In ruby you can create aliases for a method and variable name. This can be helpful if you want to override the behavior of some method without changing the origin implementation of it. alias_method take a new_name as a copy name of the old_name and it has the following syntax.

alias_attribute (new_name, old_name)

Here is a small example:

class Davi
  def capital
    puts "Karaz-a-Karak"
  end

  alias_method :orig_capital, :capital

  def capital
    puts "Karaz-a-Karak rebuild"
    orig_capital
  end
end

davi = Davi.new
davi.capital

# output
"Karaz-a-Karak rebuild"
"Karaz-a-Karak"

What is the difference between alias and alias_method

alias is more general than alias_method and can be used to create an alias for global variable, regular expression backreference (like $&) or an existing method. Class variables, local variables, instance variables and constants may not be aliased.

def khemri_city
 puts "Nehekhara"
end

alias :orig_khemri_city :khemri_city

def khemri_city
 puts "Nehekhara new"
end

khemri_city

# output
"Nehekhara"
"Nehekhara new"

alias_method must return must be called on a method. So alias is more general than alias_method.

Conclusion

It is possible with alias_method to reopen a class, override a method call and you can still use the original call. In order to maintain backward compatibility alias_method are used in plugins, extensions, deprecating variables. Alias_method can be used in Rails to define action with duplicated content and remove dublicated code.

Here the duplicated variant:

class UsersController < ApplicationController
  def home
    list
  end

  def find
    list
  end

  def search
    list
  end
end

The DRY variant:

class UsersController < ApplicationController
  def home
    list
  end

  alias_method :find, :home
  alias_method :search, :home
end

Why I use Jekyll for blogging

2011-07-03T00:00:00+02:00

For several years I wanted to write and tried many different plattforms like wordpress, blogger, or tumblr. The main problem which kept me away from writing was just the fact, that every time I want to write I just had to do it in a new environment and not in my favorite editor vim. Every system gives me the freedom to extend it in several ways but in the end it didn’t provide me the freedom to change every tiny piece I want. With jekyll I can use my favorite text editor and it really “turned me into a text monster”. This description sounds like a holy grail, but let me explain its abilities in the following sections.

What jekyll is

Jekyll is a static site generator written in ruby. It generates static html pages. The page is presented through several templates and then fires the whole site, were articles are written in a text markup language like Textile or Markdown, through the liquid converters to generate fully generated compiled website. Don’t think that it will be so easy for you to do it. First of all you have to learn either Textile or Markdown. I chose textile for writing my posts because I use Markdown to create the README files for my github account.

Setting up the environment

You need to have a valid ruby and ruby gems installation on your machine. A simple gem install jekyll will install the following gems:

directory_watcher (gives a list of files which change in some intervals)
liquid (rendering templates in a safe manner)
open4 (creates a child process to handle pid, stdout, etc.)
maruku (Markdown interpreter)
classifier (is a Bayes implementation and can be used semantic indexing like to display related post – this mechanism is used in machine learning)

To get nice syntax highlighting for your code you have to install pygments via sudo apt-get install python-pygments on Ubuntu/Debian. On the install page you can get more information about how to setup jekyll.

The directories and styles

Here is the basic layout of a typical jekyll project:

_includes: Small snippets which can be used in every place of the page.
_layouts: You can define layouts for post entries and the general default layout. Posts can have the special Yaml Front Matter.
_posts: Contains all posts in your specified markup language
_config.yml: Is a file to store configuration data like the styling of the urls, or some global variables. It is also possible to define own variables which can be used as global things on other pages.

Other files can just put on the root directory like an atom.xml file (for RSS feed) or 404.html page. For example my post.html has the following layout:

--- layout: default --- <div id="post"> {{ content }} {% include tweet.html %} <div class="clearer"></div> {% include comments.html %} </div>

The lines between --- mark a special Yaml Front Matter file. This block is treated as a special block in jekyll and can contain different components. The { {content} } stands for the content of a post entry.

Creating a layout

Here is the main template for my blog.

<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en-us"> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <title>{{ page.title }}</title> <meta name="author" content="Matthias Guenther" /> <meta name="description" content="Homepage of Matthias Guenther - software developer, writer, hiker, jogger and mobile apps lover" /> <meta name="keywords" content="software developer, writer, hiker, jogger and mobile apps lover" /> <meta name="generator" content="jekyll" /> <link href="/atom.xml" rel="alternate" title="Matthias Guenther" type="application/atom+xml" />  <link rel="stylesheet" href="/css/stylesheets/syntax.css" type="text/css" />  <link rel="stylesheet" href="/css/stylesheets/site.css" type="text/css" media="screen, projection" /> <link rel="shortcut icon" href="/images/favicon.png" type="image/x-icon" /> <script src="/js/FancyZoom.js" type="text/javascript"></script> <script src="/js/FancyZoomHTML.js" type="text/javascript"></script>  <meta name="viewport" content="user-scalable=no, width=device-width" /> <link rel="stylesheet" type="text/css" href="/css/iphone.css" media="only screen and (max-width: 470px)" /> </head> <body onLoad="setupZoom();"> <div class="site"> <a name="top"></a> <div class="title"> <a id="homelink" href="/archiv.html">&raquo; archive</a> <a id="homelink" href="/about.html">&raquo; about</a> <a id="homelink" href="/index.html">&raquo; home</a> <h1 id="sitetitle">wikimatze</h1> </div> {{ content }} <div class="clearer"></div> <div class="footer"> © Matthias Günther | <a rel="nofollow" href="{{ site.ineturl }}{{ page.url }}#top">&raquo;top</a> </div> </div> </body> </html>

I used the meta-language Sass to create my CSS. There is one problem with Sass: You have to compile it every time you made a change. Fortunately, there is the compass gem which always compiles my sass file when I change it. When I build my page I started with compass watch css/ & a command to automate Sass building. This is very handy when changing the layout.

Static webpages – how to include dynamic content

Jekyll only creates static webpages but with the help of Javascript it is possible to add a Disqus comment platform. You just have to create an account and then use the following snippet:

<div id="disqus_thread"></div> <script type="text/javascript"> /* * * CONFIGURATION VARIABLES: EDIT BEFORE PASTING INTO YOUR WEBPAGE * * */ var disqus_shortname = 'wikimatze'; // required: replace example with your forum shortname // The following are highly recommended additional parameters. Remove the slashes in front to use. // var disqus_identifier = 'unique_dynamic_id_1234'; // var disqus_url = 'http://example.com/permalink-to-page.html'; /* * * DON'T EDIT BELOW THIS LINE * * */ (function() { var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); })(); </script> <noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript> <a href="http://disqus.com" class="dsq-brlink">blog comments powered by <span class="logo-disqus">Disqus</span></a>

It is best to put this piece of code in an extra file under your _includes directory and then add it in your template for posts. Now the comment function is available in all your posts.

Deployment

There is a bunch of deployment strategies: rsync, ftp, Rack-Jekyll (deploy on Heroku, EC2, etc.). I prefer ftp (with the glynn) because it was easy to install and worked great with my server configuration in my _config.yml.

Conclusion

Just look on other pages what is possible with Jekyll. You can learn many new things by looking at other jekyll blogs and copy what you need. I love to write a little bit and after I finished an article just perform rake deploy to upload my blog.

wikimatze

Searching Haml files with ack

Questions to answer

Solve problems .ackrc

Further refinements

Further reading

Installing PostgreSQL gem under Ubuntu and Mac

The problem

Solution for Mac

Solution for Ubuntu/Linux

Conclusion

Compiling Vim from source for Ubuntu and Mac with ruby and python support

Install rbenv

Get the latest version of Python

Get the latest version of Vim

Compiling Vim and gvim

Check the installation

Installing MacVim from source

Conclusion

Further reading

SMART principle

Putting theory into practice

Cost for SMART

Conclusion

Global Coderetreat 2011 in Berlin

Setting up goals

Conclusion

Further reading

Benefits of Scala

Main facts about Scala

Conclusion

Further reading

Mail Client in Java

Images

Installation for Netbeans

Conclusion

Further reading

Benefits of reading a book - and use it right after that

What you should do during the process of reading

Benefits of note taking

Conclusion

Further reading

Why learning a new programming language

In the beginning there was Turbo Pascal

Then Java came …

Enlightenment with Ruby

Automating tasks

Head scratching with Scala

Conclusion

Further reading

Method alias in ruby

What is the difference between alias and alias_method

Conclusion

Further reading

Why I use Jekyll for blogging

What jekyll is

Setting up the environment

The directories and styles

Creating a layout

Static webpages – how to include dynamic content

Deployment

Conclusion