IFL 2007 - Day 2

Today only three sessions took place due to the excursion (a nice visit of Geldermann-Sektkellerei...). The first was about contracts, the second about Algorithms and Data Structures and the last one about Foundations. My talk was part of the second session, you can download it here: Graph Parser Combinators

My key learnings have been:

• Malcolm Wallace: polyparse, commit is the principle dual to try known from parsec, parsing can be done lazily

After my talk I got several advices:

• Why are (graph) parser combinators so powerful? They are aware of a context! Thus they are more powerful than general-purpose parsers for context-free languages. Thank you Malcolm for pointing this out!


• I have to try to generalize my approach such that it is usable for a broader range of problems (advice by Frank Huch).


• I should try not to pass the active node that much but instead should really try to hide it within the monad.


• A parser type should not depend on lists of tokens. I learned that Malcolm already abstracted from lists in a current version of polyparse (via type classes).

IFL 2007 - Day 1

Today four different sessions took place at IFL'07: Compilation I, Applications I, Parallelism I and Types I. Some comments and learnings below:

• Jeroen Fokker: Essential Haskell Compiler, a talk about constructing a fully-fledged Haskell compiler in a very modular manner using a chain of transformations and generative technologies, nice for teaching, because modules are very specialized and concise, easy to add transformations


• Neil Mitchell: Supero, shows how to boost the runtime-performance of Haskell programs, Haskell programs can perform nearly as good as C programs although they are formulated on a far higher level


• Rinus Plasmeijer: i-Tasks, a library to compose workflows automatically providing the corresponding web interface, remembers me a little bit to the Synthesizer Generator of Reps and Teitelbaum that derives structured editors from data types or the Editor Combinators of Kahl et al.

People here are very nice so I am looking forward to my talk tomorrow!

IFL 2007

I want to invite you to watch my talk at IFL 2007. It will take place at September 28, 2007 and its about Graph Parser Combinators, one of my current research projects.

See you in Freiburg!

Linie mit Knickpunkten

Wo nur liegt die ästhetische Mitte einer Linie mit Knickpunkten (also einer Zickzacklinie). Solch eine Linie besteht aus mehreren hintereinanderfolgenden Segmenten. Es gibt derart viele in Frage kommende Punkte, z.B.

• Mitte des Pfades, also exakte Mitte der Gesamtstrecke


• Mitte des mittleren Segments, bzw. wenn nicht vorhanden mittlerer Knickpunkt


• Mitte des Segments, in dem die Mitte des Pfades liegt


• Schnittpunkt mit Mittelsenkrechter der Strecke zwischen den beiden Endpunkten


• nächstliegender Punkt auf der Linie zum Mittelpunkt der Endpunkte


• Mitte des nächstliegenden Segmentes


• ...

Aber wo ist denn nun die ästhetische Mitte? Ich stelle demnächst hier mal Screenshots ein und lasse abstimmen :-)

Konkret geht es übrigens um eine UML-Assoziation mit Knickpunkten. Nun soll ein Label mit dem Namen der Assoziation möglichst hübsch positioniert werden...