wicked source

What is Forth? - Forth is a pretty old programming language! As we all know, programming languages just get better directly proportional to wine. That's why I recently started to learn Forth. However, the so-far learning experience had no taste of my favorite wine in it, it rather made me whine and cry. That's to some extent due to Forth's basic strangeness as it's a stack-based, concatenative language but the lack of detailed explanations in my learning resources have played quite a role, too. Just recently I have discovered Starting Forth which is a nice online Forth introduction. It helped me a lot to understand Forth's fundamental words of POSTPONE, IMMEDIATE and LITERAL which are used in Forth's "grey" area of compilation vs. interpretation semantics. Starting Forth should be your choice if you want to study Forth. Anyway, flashed with my new Forth knowledge I decided to collect my findings on those exciting words for my fellow to-be-born Forth comrades so that they may find their way to Forth illumination earlier than I did; this is my legacy for you!

1.1 IMMEDIATE

You can use IMMEDIATE to change the compilation semantics of the last defined word to be equal to the interpretation semantics. In the below example that means that [FOO] already is executed upon bar's compilation.

: [FOO] ( -- ) 5 . ; immediate [FOO] : bar ( -- ) [FOO] ; bar see bar

1.2 : ; [ and ]

: switches into compile state and ; switches back to interpret state. They contain the factors ] (switch to compile state) and [ (switch to interpret state), that do nothing but switch the state.

: xxx ( -- ) [ 5 . ] ; xxx see xxx

It is worth mentioning that ; expects the data stack to be empty, usually. Otherwise an "unstructured" exception gets thrown.

1.3 POSTPONE

POSTPONE has different effects. Either it gets called on an immediate word or on a word which isn't immediate.

1.3.1 POSTPONE and immediate words

That's the easy case. Called on an immediate word POSTPONE just undos the "immediate nature" of that word.

: SAY-HELLO ." Hello" ; IMMEDIATE : GREET1 SAY-HELLO ." I speak Forth " ; \ upon compilation "Hello" is printed : GREET2 POSTPONE SAY-HELLO ." I speak Forth " ; \ nothing is printed upon compilation. On execution both strings are printed.

1.3.2 POSTPONE and not so immediate words

POSTPONE finds the address of the next word in the definition (in the below case it is x) and compiles its address into the compilee (y) definition.

: x + ; : y postpone x ; immediate see y \ : y 140635553271192 compile, ; immediate ok : z ( n1 n2 -- n3 ) y ; 8 3 z .

In the definition of y POSTPONE is called on x which is a non- immediate-word. As a result, the address of + and the word "compile," are compiled into y. I made y immediate so that during the definition of z y gets executed immediately so that "140635553271192 compile," is run, which compiles the addition function into z.

1.4 LITERAL

LITERAL is an immediate word. During the compilation of a word x its effect consists of consuming a number from the stack; when x is run LITERAL then pushes that number onto the stack.

#FUN-FACT: The runtime part of literal (its word is (LITERAL)) is often used without really knowing. In the following example bla just pushes 5 onto the stack - what gets compiled into bla behind the scenes is the "run-time code for LITERAL" (the mentioned (LITERAL)) and just then the number itself.

: bla 5 ;

Have a look at the definition of LITERAL. It compiles the address of the run-time pushing code with POSTPONE and then compiles a number with ",". Consequently, a resulting compilee's compiled code just pushes that number onto the stack.

: LITERAL POSTPONE (LITERAL) , ; IMMEDIATE \ Gforth does not know (LITERAL)

1.5 Case Study - IMMEDIATE, POSTPONE and LITERAL in the wild

: x 5 ; immediate : y x ; \ unstructured! \ Using POSTPONE : y postpone x ; \ Using LITERAL : y x literal ;

For : y x ; we get an exception since the word ; finds 5 on the data stack, the stack should be empty, though. There are two ways how to solve our problem.

Using POSTPONE: With POSTPONE we can easily undo the immediate effect of x. As a result, x gets compiled into y like a "normal" word.

I have recently finished a university course dealing with distributed computing on top of the OpenStack platform. Among other tasks, I had to create a project realizing distributed testing featuring the OpenStack scaling facilities. Anyway, you can get the code on https://github.com/sleepomeno/DistributedTestingOpenstack. It uses the http://www.mozartspaces.org/ implementation as middleware. The goal is to get the tests started by mvn test executed on OpenStack.

Today I've made a visit to my local bookstore, heading to the books-by-author shelves. Found a David-Foster-Wallace book I hadn't seen so far: "Consider the Lobster" (in German: "Am Beispiel des Hummers"). It's a report DFW wrote for a gourmet magazine about the Maine Lobster Festival. Lobsters get boiled alive, is that evil or too evil to tolerate? - It's not surprising that this book isn't rocket science (or whatever the literary pendant is), after all it's just a report.

After some browsing the net, I noticed that the English edition "Consider the lobster" is a collection of diverse DFW reports whereas the German version only features that specific report. Obviously, the German reading majority is considered so desperate for some DFW material that they'd pay the 7 Euro for that single, average report.

I've watched "Man of Steel" today - you know, the current Superman film. I better shouldn't have done that.

Retelling super hero stories has been a great trend lately (just remember Batman or Spider Man), some actually quite entertaining (=> Batman), some a little bit awkward (=> Spider Man) and all of them being box office successes. Well, I guess "Man of Steel" lines up nicely in the box office respect and still introduces another category of super hero filming: the absolutely dispensable, useless warming up of old Superman material in a remarkable inept bad-style fashion!

It may be my mistake having expected something more than a mosaic of common Superman history, rearranging enemies and story line building blocks of former Superman films. I thought that they'd come up with something new. Instead they retell us the story of Krypton and how the planet fell apart for a good half an hour - at least there are some (unintendedly) funny scenes like the one in which Jor-El flees on top of a creature seemingly escaped from an Avatar filming set.

It goes without saying that the Louis Lane story line is neither creative nor romantic nor suprising; actually, the only suprising thing about the whole film is the fact that it doesn't feature the American president giving impotent orders to attack the superior Krypton delinquents. There is no president, just some cliché general with a slight sense of humour. (Overall, there is very little humour in the whole movie. That's a pity as comic screen adaptions generally do well taking themselves not too serious!)

Again it's time to start reading "Infinite Jest" as I've never finished it so far. This summer should provide enough time to accomplish that, anyway, I should be finished on September 12th as this will be the 5-year anniversary date of the author's, David Foster Wallace's, suicide.

You know that problem? You create a new class and in the comment above the class it says "@author NAME" - but unfortunately NAME is not the real name you would like have in that comment?! Obviously, Eclipse derives that NAME from the user of the current session (at least on Ubuntu). That's not my firstname+last name, though. So it has been very often that I changed that NAME by hand - always a little bit annoyed. It goes without saying that it would be nicer to make Eclipse fill in the wanted name in the first place. How do you do it? Two possibilities:

Go to Window -> Preferences -> Java -> Editor -> Templates. Change @{user} to your name.

Google has launched a notes-taking service: Google Keep. 

Is it better than Evernote? All in all, probably not. However, Google Keep has a significant advantage: I like using it!

When I once looked at the Evernote Android app some time ago I saw an app with a ton of features. There was a dashboard layout linking to all the different note types Evernote supports... all of that looked somehow administrative and felt inherently slow. That's where Google Keep shines - it has a simpler (especially the web version!), a more responsive UI and makes notes taking especially easy.

Obviously, there are features missing which would suit well to a notes taking app power by Google - for example collaboration. Still, it has already proven to be more useful to me than any other online notes taking app - I even created a notes list for possible blog entry topics! Who knows, Keep might have a good influence on my blogging rate.. ;)

I have just stumbled upon these amazing lecture "slides" of a novice Haskell course at the University of Virginia: http://shuklan.com/haskell/ 

No Powerpoint slides but fancy HTML5-driven slides! The framework http://lab.hakim.se/reveal-js/ provides the magic behind it - the animations, the transitions and the structuring. I also like the idea of providing extra information in the Console window - which is especially handy during a presentation where the audience can only see the projected slides while the presenter can see the extra information in the console window.

All in all, Powerpoint can probably do all the animation-stuffy things that reveal.js can do (and a lot of unnessary things!!), however, the added value of HTML5 slides is the sole fact that they run in the browser! Every slide has an URL - you can reference them! You do not need Powerpoint to watch it! And just imagine the possibilities for collaboration if there was a per-slide commenting capability or other things... (+1'ing a slide anyone?!)

Today I present two nice key shortcut timesavers I have just stumbled upon:

"Insert Line Above Current Line" - Shift-Ctrl-Enter

"Insert Line Below Current Line" - Shift-Enter

Those shortcuts might not seem too exciting at first glance, however, they might stop you from wasting a lot of time!

They really shine when you are in the middle of a line at the moment - in order to start inserting a new line below the current line you would need to go to the end of the line by pressing End and then press Enter. That's two key strokes and above all, End is very awkward to hit  on most keyboards. (There might be a scenario in which you get there by just pressing Down but if you're in the middle of the line and/or there is not a line below the current one yet it just doesn't work!) Even worse, you might be tempted to use the mouse to get to the end of the line, which is the worst thing to do from a productivity-centered point of view ;)

People's opinions about Windows 8 are quite diverging and after using it for a day I haven't made my mind up so far. One thing's sure, though: Windows 8 Boot time is great! It takes roughly 5 seconds until the login screen appears on my notebook!